I dont think so. It's not even possible in GT5 to map the TH8rs in sequential mode as handbrake.
That one is mapped the same as the left and right shifter paddle.
Any controller what PS3 recognizes as a controller can be mapped as handbrake.
PS3 doesn't recognize keyboard as a Controller, it recognizes it as a HID Device.. Big difference.That is not true, for example i bought a USB keyboard to wire up my handbrake with. It responds in PS3 menu´s and in GT5 menu´s, but once you get on the track it stops responding. I read somewhere (afterwards) that only DS3 controlers and Wheels will have inputs that can be used on track, other controlers will only Work in menu´s - as I expirienced.