I guess it's possible but doesn't make a whole lot of sense for the reason stated.
York interacts with the OPP, Durham and South Simcoe police via radio patch more frequently than with TPS so it just seems like that might not be the reason.
The last few times I've heard an emergency button activation I did notice they are no longer using the Code 100 and instead were using 10-33. During the tornadoes last week the dispatch was voiced as respond to a major disaster instead of the code 500. Haven't heard any of the other 100's series code calls lately (100 officer needs assistance, 200 emergency calls only, 300 armed/barricaded suspect/hostage, 400 bomb and 500 major disaster incl aircraft).
I'll see if any of my sources might be able to shed additional light on this subject one way or the other. As I said, change is likely but not to accomodate TPS. Normally when there is any intercommunication they just dump codes completely anyway.