Uniden firmware update tool: BC_VUP_v2.0.0.7.exe
Uniden BR330T firmware: BR330T_V1_06_02.scn

http://info.uniden.com/twiki/bin/view/UnidenMan4/BR330TFirmwareUpdate

Connect UBC-3500XLT to PC and set it to Firmware update mode: power+L/O+6

Start BC_VUP and it checks the scanner model by sending cmd *MDL\r and stops with msg: Model is not BR330T.
MDL cmd returns UBC3500XLT.

Rename BR330T_V1_06_02.scn to UBC3500XLT_V1_06_02.scn.

This may work and maybe the BR330T firmware is flashed into UBC-3500XLT and maybe UBC-3500XLT starts after this procedure?!

I only have one UBC-3500XLT, but if I get another then I maybe try this. Probably the UBC-3500XLT won't start or work properly after fw flash. Try at your own risk !!