At the hearing the parties filed the following statement of the dispute and joint statement of fact and issues:

It appears to be common ground that Carman Jessup was in fact given two separate relief assignments as a relieving foreman. The first was on Friday, May 5, when he worked at North Bay in relief of a foreman who was absent due to illness that day. The second was from May 8 through May 12, when he again worked as a relief foreman, on that occasion at Rouyn. It is not disputed that Saturday and Sunday, falling between the two assignments, were Mr. Jessup's normal days off.

The Brotherhood's claim relies, in part, on Rules 24.1 and 27.1 of the collective agreement which are as follows:

The Union also relies on the provisions of the parties' Memorandum of Understanding Regarding Auxiliary Service. Under that agreement cranesmen, carmen and carmen's helpers are selected, on the basis of seniority, for placement on the auxiliary call list in the event of a need for unforeseen overtime work. It is not disputed that Mr. Jessup is on the auxiliary list and would normally have been entitled to be called for overtime work, in accordance with the terms of the Memorandum. The thrust of the Union's position, however, is that as an individual who had accepted temporary promotion to supervisor's work, Mr. Jessup forfeited his eligibility for overtime work within the bargaining unit, and the Company violated the agreement by, in effect, assigning overtime work to a non-bargaining unit employee.

As a general matter it appears to the Arbitrator that the Union's position is well founded in principle. If it can be shown that an employee has accepted a temporary promotion into a supervisory position for a definite period of time, it would follow that during that time the individual so scheduled can no longer be entitled to the rights of a bargaining unit employee within the collective agreement, save as they may otherwise be spelled out in its specific terms. For example, Rule 23.27 of the collective agreement makes provision for the return to the bargaining unit for a person temporarily promoted to an official or accepted position. In the Arbitrator's view it is significant that that rule further provides that the Company provide to the Union such particulars as the expected duration of a temporary promotion. Such provisions are consistent with the Union's argument that an employee temporarily promoted to a supervisory position necessarily forfeits certain rights which would otherwise be available to him or her under the collective agreement. It would therefore seem inescapable that an individual who is scheduled to fill a supervisory position on, for example, a thirty day relief assignment, leaves the bargaining unit for all practical purposes during the course of that period.

In the instant case, however, the facts are not so straightforward. Bearing in mind it is the Union which has the burden of proof, the Arbitrator has reason to doubt the merit of its claim on the facts of this case. While the Union's representative seeks to characterize the circumstance of Mr. Jessup as a single temporary promotion to relief foreman, from May 5 to May 12 inclusive, on closer scrutiny, the facts reveal themselves to be otherwise. On balance, I am compelled to accept the Company's characterization of what transpired. In fact Mr. Jessup was given two separate temporary relief assignments. The first, confined to May 5, was in North Bay in relief of a foreman absent due to illness. That assignment must, in my view, be taken to have been concluded as of the end of the working day of May 5. Thereafter, Mr. Jessup was assigned to a separate relief assignment in Rouyn, from May 8 to May 12 inclusive.

If, in fact, Mr. Jessup bad been temporarily promoted prior to May 5, or had been so advised in advance, with an understanding that he would be a relief foreman covering the two separate assignments during the period in question, the Brotherhood's case would be more compelling. The evidence necessary to establish that critical fact, however, is not before me. As in any arbitration, where the evidence in respect of a critical element of fact is unproved, the absence of such evidence must weigh against the party bearing the burden of proof. In the circumstances of this case, therefore, I cannot conclude, on the balance of probabilities, that prior to May 5 Mr. Jessup was promoted to relief foreman on the understanding that be would cover two separate assignments during one single temporary promotion. On the contrary, I must find that the Union has not proved that the treatment of Mr. Jessup was other than the completion of two separate and unrelated relief assignments. That being the case, having completed one temporary promotion assignment at the conclusion of May 5, Mr. Jessup would have reverted to his rights under the collective agreement prior to the commencement of a second and separate temporary promotion commencing May 8. On the facts so found, he remained entitled to his rights under the collective agreement as well as the memorandum governing auxiliary service during his regularly scheduled days off, May 6 & 7. For the purposes of clarity, having regard to the reasons related above, the Arbitrator's conclusions might have been entirely otherwise had the evidence confirmed a single and unbroken period of temporary promotion from May 5 through May 12. As it does not, the grievance must be dismissed.