As anyone with a Nortel GPSTM knows, it's a close cousin to the Thunderbolt but not exactly identical. Notably, coming from a CDMA environment, the unit has an "even second" output, aka PP2S, aka 0.5pps, aka 0.5Hz, etc. (Hoping to make this searchable...) There are software commands to configure this on the Thunderbolt too, but the GPSTM appears to have this function hard-coded into the PAL, and it can't be set back to PPS in software.
However, there exists a PPS signal on the PCB, at TP13 between the Trimble chip and the PAL, discovered by some folks at the hackerspace here, during some noodling-around with an oscilloscope this afternoon. It's all documented here:
https://www.i3detroit.org/wiki/Nortel_GPSTM
This is for a NTBW50AA-11 module (single long board), other parts may have the signal in different places but I bet it's in there. 
Enjoy!-Nate B-
