Here is what I know:

The original 3.9BL allowed unlocking. How?

Then came a newer 4.6BL that could not be unlocked until geohot's miracle.

I was using iPlus to unlock and downgrade my 4.6BL to 3.9FB. I had the seemingly standard problem where I had to run through it twice.

When I restored the 1.1.4 after having the 3.9FB I noticed that even though the phone was still not activated or jailbroken, I could see the phone was unlocked because it connected to T-Mobile.

So, how was that possible?

Why is the 3.9FB or regular 3.9BL safer to have than the 4.6BL if either can be unlocked? (know the 3.9 is desirable to keep the BB matching the firmware)

beacuse 3.9 is old territory and is more familer than 4.6 thats plus ziphone had a nasty habbit of downgrading bootloaders so that was also put in places so that people could downgrade safely if they wanted and upgrade when a way becomes available, read the iplus sticky for more info

yeah i am on original 3.9 and when i restorted to 1.1.4 it was still unlocked but it wasnt jailbroken.

another good reading on BL here

dude..

its very much possible if u didnt virginize. For example, i start off on 1.0.2 and virginize then run anysim. Even if i upgrade back to w.e. version, it will still have the changes made by anysim, and vice versa. IF i downgrade to 1.1.1. or 1.0.2 i will still be unlocked, unless u truly erase the bL and reapply the unlock