I think that product it's just a collection of alternative models that replace the default ones so, there shouldn't be any specific problems, since GSX removes every default ground vehicle placed on a parking as soon you select it.
The only thing that *might* cause a problem, is that this product will probably alter the default airport vehicles .BGL file, located at FSX\Scenery\Global\Scenery\vehicles_airport.bgl
Since the GSX installer patches it, in order to disable the default Pushback tractor (which can't be disabled in any other way, the Pushback it's a special case), it's likely it will have troubles patching the file which is not original anymore, so you'll might get a warning by the installer that patching was unsuccessful, and you'll still see default Pushback vehicles or, more likely, their replacements.