I have not looked into the details of that API to get tower information.
I am pretty sure you can't force your blackberry to a specific tower.
From what I understand, your blackberry sends its signal strength readings to the network and the network can see your signal strength. The network then decides if it wants to hand you over to a new tower, not your device. The only thing your device can do is adjust its gain (signal gain).. and I don't think there is an api to adjust this, it is automatically adjusted based on incoming signal strength.
Would be neat to have an app show how many towers are within range though, but not sure how useful it would be. I know you can get this info from the engineering screens..
This is not possible with the API.. I dont know if you can even get a list of in range WIFI access points.. As far as I can tell, you can only get info about a tower or access point that your BB is currently connected to.