Thanks for reporting this issue to the group Mark.
Thanks for catching this, I believe you can get it work by modifying the debug settings to connect to tty instead of COM. Since MacOSX and Linux do not get COM ports. Not sure if you tried this and you have mentioned the same.
As mentioned above, manually setting using the COM port in the
Tracing Setup dialog still results in
Error: Error opening UART transport
Prior to OSX 10.10.4 this issue was not present