So does anybody have any solutions to this problem. To summarise...
I have FlyTampa CYYZ purchased from Orbx, thus no encrypted files. I have CYYZ disabled in the GSX jetway list. Various service vehicles are invisible... catering trucks, pushback vehicle, UHD containers and trucks, although their actual presence, albeit invisible, can be inferred from GSX messages, doors opening, lifts ascending, and the a/c being pushed back.
So really GSX cannot be used at FlyTampa CYYZ, and I'm better off using FS2Crew Pushback express. Obviously I've purchased GSX Pro, and since CYYZ is my home airport, I really need it working correctly at Toronto Pearson. I also believe that the problems being caused at CYYZ by GSX, are impacting the display of my arrival airport... KORD, with buildings being invisible there.