Outcome unclear, ask again later.
That said, there would likely be clauses written into the wireless network sharing agreement between Rogers and MTS that cover the unwinding of that agreement in the event of sale of either side. This would be similar to how there is a $120 million break fee if the Bell takeover of MTS does not proceed. Who receives that money would be based on while the deal fails.
What I can see happening is that the new Bell entity will have to maintainin the existing sharing agreement with Rogers. Once that expires...they will probably get Rogers to lease access to their network instead.