I received this initiation from Kundeling Rinpoche and he tells us that Je Tze Jin Ma was a form of Tsongkhapa revealed to one of the previous incarnations of Dagom Rinpoche; therefore, this practice is very close and special to Dagom Rinpoche and his students.
Apart from the mantra, (om ah guru sumati kirti aparamita ayurjnana siddhi hum hum), there is also a special form of Migtsema associated:
Mig me tze wai ter chen chen re zig
dri me khyen pai wang po jam pel yang
du min tze wai jom dze tze pag mey
gang chen kay pay tsug gyen tsong kha pa
lo zang drag pay shab la sol wa deb.
Basically, the supplication switches out the line about Vajrapani, and extols Tsongkhapa as the essence of Amitayus, or Tze pag mey.
I may see Kyabje Yongyal Rinpoche this week or next, I will request Rinpoche to give more explanation on Je Tze Jin Ma and report back.