some carriers do not support (or disable) GPS functionality at the cell towers. my former carrier does this, so check with your carrier first to see if they actually support GPS services.
However, saying that:
1) on the rare occasion, bbmaps would work, but far more often it couldn't get any sats
2) google maps would only use cell towers to triangulate on my pearl (not true GPS, just a guess like OP's), but on my friends HTC Touch Diamond using the same carrier I was on google maps worked great!