To me, that's the best case for a couple of reasons.
The central infrastructure is already present. Adding towers to the smartzone system is as simple as literally building a tower, stuffing some quantars in a shack, and tying it all in to the zone controller. And the tower sites needn't all be in one band. You can be on 800 and I can have a 400 system, and someone else can do VHF - so those agencies with radios that are already Smartzone capable but not necessarily in the 800 band, can just get by with a flash upgrade instead of having to get all new kit (like my VFD will).
Granted, I know very little about M/A-COM systems, especially multi-site installations, but it would be my understanding (from my limited knowledge of ECOMM WARS in the Vancouver area, etc) that an EDACS multi-site system is a big hassle. Furthermore, and this is possibly because I don't live in an area with a large EDACS system, but I seem to see a lot more accessories and equipment designed around the Motorola platform than M/A-COM, especially for emergency services.
I heard a rumor that one of the entities in the Calgary Regional Partnership once priced out costs to build and install the infrastructure required to expand 753f into their own region. It worked out to about $5m - not per tower site, for the whole thing. That to me is a surprisingly low amount.
Also, there are already a number of cities using Motorola trunking equipment which could be consolidated into a provincewide system. Red Deer, for one; and IIRC either the Hat or Lethbridge still has a Type I/IIi system running their public works. Again, I grant you that three examples does not make an overwhelming majority, considering both Edmonton and Lethbridge run M/A-COM. And I'm sure there are several systems throughout the province that people have no inkling of yet (or aren't sharing with us RR folks!). I also suppose there's got to be some way of interlinking M/A-COM and Motorola, so that well-established systems like Edmonton wouldn't have to be completely scrapped.
I do admit I have a little bit of local bias in me, as I'm sure the folks up Edmonton way (or down in Lethbridge) do, favoring my/their own local system. To be quite honest, I'm not absolutely dead set against something other than a Motorola system being the final decision, other than the fact that it will screw scanner listeners out of some good comms. (Presuming no compatible scanner will be available by then - I don't agree with the folks who say there will NEVER be one capable of doing trunk protocol XYZ - but that's another topic for another entire thread.) So long as the radio works and covers all the area that it needs to, I'd be happy.