Currently, the regions served by GO train are: Durham, York, Simcoe, Peel, Halton,Wellington, Waterloo. The separate cites that have GO train are: Hamilton and Toronto. If you added GO bus to that mix, you would also have: Northumberland, Peterbourough, Kawatha Lakes, Dufferin, Brant, and Niargara.
Should all those disappear? No. My idea is only for transit, not for everything else that is covered by the regions/counties. Think of it as Metrolinx now is in charge of all transit. The livery could change, or not if they see fit. Metrolinx would be the one deciding on where and what transit improvements happen. And, of course, they would be asking for some property taxes.