Looking at your script file again, looks like you also changed line 371, from
float dx = 250.f, dy = 0.f, dz = 0.f;
to
float dx = 0.f, dy = 0.f, dz = 0.f;
Maybe that's causing the issue?
Could you upload your LAFireStationStart.script file?
I'm actually not sure exactly how the original LA Mod deals with spawning the Tiller in the station at start. Looks like there's the script that checks for vehicles at the map fire vehicle spawn to either add or delete the trailer, but nothing else seems implemented, as far as I can see. The Tiller isn't even set to spawn by default, just the Tower, and while the instructions say to change the prototype referenced there, there's nothing that would spawn the trailer.