Interesting writeup. The upgrade/switch is a very political thing and there is a ton of money behind it. There seems to be a lot of info left out of the article but still a good overview of some of the challenges.
The theory is that most of the current radios are suppose to work with the Harris system. I have been told that they (Harris) has already been changing out the Motorola repeaters with their own gear.
So after reading the article again I does say something about any radio will work as long as it is P25. so it should let the entities be able to get different brand of radios and not be stuck with buy Motorola if I am reading it right