For folks wanting the internet connection to come up on BT connection, I suppose one might be able to get away with inserting an "/sbin/ifconfig gprs0 up" at the end of every bnepX "add" action in udev's bnep.rules file. I haven't tried it for three reasons:
1) I switch between Wifi and GPRS pretty often, and figuring out which is optimal and appropriate is something I normally handle by getting out the N900 anyways,
2) My "solution" for such problems involves having sshd and x11vnc running and
3) I pretty much never disconnect.

Warning: the above ifconfig/udev advice is entirely theoretical; I haven't even attempted to see what happens when running that command, let alone test that configuration. If it works, then, hey, great!

As an alternative, maybe there's some arcane dbus command one can have run that tells the n900 "hey, make with the internets now" or something. I wouldn't know offhand, but it might be something to look for.


and on a side note, it is so totally awesome that this setup is still helping folks.