It's interesting that the form for transferring your license to the new Part 61 license, does not ask for whether you have passes in a BGT theory course or not. Those who already fly turbine powered aircraft only need to tick the box
Gas Turbine Engine in the
Design Features section, and are required to provided evidence in the form of;
* Certified true copies of logbook pages showing entries for an aircraft flown that has the Design Features applied for
* Certified true copy of an aircraft rating on a foreign licence if applicable
* Certified true copy of training records for an aircraft with Design Features applied for
Here is the form required:
Part61-9TX