Taking a sound engineer wouldnt really help.
I have similar issues and ive been in broadcast sound for 29 years!
Scanning your g3 would only help if the transmitter that they are using was also a sennheiser. then you could find the transmitter freq and couple into it. Chances are it isn’t – why
because
1) Theyre probably cheao skates and went with the cheapest option they could
2) There are infact many other manufacturers of radio mics out there
3) Cant think of 3.
Bottom line. If there isnt an available output socket, or its inaccessible then you can’t – so do what i do.
Never use anyone elses kit! It will be rubbish anyway and probably fail, be wrongly configured, pop like mad, be riddled with interference and hum, and be generally unsatisfactory.
I take multiple radios to a wedding. 3 speeches = 3 personal g3. 4 speeches = 4 etc etc. – up to 6 then i struggle.
Peter
Post Production Dubbing Mixer