have just successfully upgraded my telecom branded modem to a bt beta firmware and everything seems fine on my snap dsl connection.
managed to ask very nicely the nice chap Bill from http://bt2700hgv.tripod.com/ir1002700HGV.htm for one of the beta firmwares that he wasnt going to make public due to not knowing which of the 2 files he got did what so i asked to test for him.
things went smoothly except for needing to apply a view source/edit source/apply changes with opera to make it take the snap realm.
please keep an eye out on the website as he will be formatting my ramblings into instructions and make the file available shortly. if you have a leet mailbox (17mb+mime overhead) i can send you a copy, hit me with a pm if you cant wait.
all care no responsibility of course, this is the internet and anything can go wrong.
i can only assume there are a few out there that want to 'jailbreak' these things.
##update##
Runs well, missing a few of the telecom firmware bits and pieces like internet filtering and time of day surfing etc etc. seems stable enough and gets slightly better line speeds than the many times hacked g604t. we will keep on researching on ways to go onwards and upwards. but this guineapig is pretty damn happy.