Here's a good
tutorial on GPS vs aGPS - I didn't know much about it before I read it. Whether this would incur a data charge when I'm roaming in Canada depends on a) what aGPS configuration the vogue works on, and b) whether the cell tower - phone communication occurs over the data line or not. Your testing would suggest that the cell tower "assistance" is using a data route.
I turned off aGPS by using a program called Advanced Config. It is included in many custom roms, can be dl'd too. I also turn off my data when I go to canada by preventing data while roaming - for reasons other than just the aGPS. The only thing I've found with iGo8 is that with aGPS and data off, I typically need to soft reset before using it or it won't get a lock, don't know if this is because it is trying to use old sat info, or because I just got impatient the first couple of times and then began soft resetting after that. But yeah, I would get a lock in about 2-4 minutes with that config, and dropped sats about every 10 mins for 20 seconds or so.
But your testing might also indicate that I don't kneed to turn off aGPS, I can probably just block my data connection and have the same results. I thought that maybe the phone would be "searching" for that assisted information and then maybe not function at all; apparently that's not the case.
Definitely while I'm home in the US I keep aGPS on, and have seconds to a sat lock and almost never drop a signal. I only disabled it cause I was going to Canada.
I did not try simply disabling data but leaving aGPS on, as I assumed it wouldn't work anyways. The next time I go to Canada, I will give this a try, and see if I lose satellites all the time and/or if my TTFF dramatically improves; from what you say, though, it's probably the equivalent of turing aGPS off.