I myself wouldn't have gone with a new system yet. If I understand things right, though, the plan was already in motion prior to AFRRCS being announced, which is (may be) part of the reason it went through.
I also heard that the users were told that it was P25 compatible, which is, of course, untrue. Going with a P25 compatible system now would mean migration to, or piggybacking onto, the AFRRCS network would be easier later on.
There was/is a group called the Calgary Regional Partnership which is/was comprised of several municipalities around Calgary, as well as the city itself. Just before AFRRCS was announced, and I mean literally just before, the rumor is that the CRP was ready to put pen to paper to approve an expansion of the Calgary digital trunk radio system, sysid 753f, to cover the entire region. That was put off, obviously.
One thing to remember is that AFRRCS is not a mandatory system. First responder groups won't HAVE to go to it. I would suspect that most will, but there's nothing that says that agencies have to use AFRRCS. You may still see, for example, Yellowhead County's MPT1327 system, or Wheatland's new MotoTRBO network, optionally with links to connect it to AFRRCS. The province has said it doesn't want to put TOO many "links" in the network, meaning (in my opinion) that it's trying to dissuade the creation of a network of small, non-interoperable networks - since one of the main goals of AFRRCS is to enable interoperability.
To sum up, I don't know why Wheatland went digital, especially not now, and with the system they chose. I know that it wouldn't have been my choice, had I been the one to make it. In fact, my department's direction right now is to keep partnering with the City of Calgary, and buying radios compatible with their system - which are, in many cases, fully compatible with the proposed P25 700MHz provincial system as well.