Sports car spawn?

[Cohort]

I downloaded three mods for the Attrazione, Temptressa and Vortex. They are XTBL files and I opened them with Notepad. Inside I found the line "<ParkingSpawn>1</ParkingSpawn>" for all three except the Attrazione had another line "<ParkingSpawn>0</ParkingSpawn>". I changed the values to 100, 10, 9, and 2, but then I stopped seeing any of the three cars.
Do these lines change the spawn rate of those cars? If these have little to do with spawn rates, is there any way for me to increase the spawn rate of those cars?

 

[Gondar]

Apparently no. The xtbls are completely and utterly ignored. They're compiled into binary files instead, packed in str2s. Yeah, I thought it'd be that simple myself.

And for what it's worth, it may not actually BE paying attention to the packed files anyways. It certainly doesn't seem to care about the variants for the purposes of gang spawning, so I'm suspecting there's some nastily hard-coded stuff in the game (as in maybe packed into the exe itself) and the files are only partly used.