Something else to keep in mind is that your friend might have "cheap unlimited data" that dates back to when that feature was available for phones before they were "smart". Odds are pretty good that unless your friend's phone is an iPhone or Blackberry that ends with two zeros in the model number that they are not on the "new" network and would need to change plans regardless.

As for the hardware requirements, MTS and Rogers share the HSPA (4G) network however they will be running different LTE networks. With that in mind, if you buy a phone that will work on Rogers in Manitoba today it will work on MTS provided it is not carrier locked. Sadly, most phones are carrier locked by default.

If you want more specific advice I would be willing to answer questions privately. Knowning the model number of the phone and a "not more than" price on the plan would be helpful though.