I’ve seen this a few places. Are they actually AR-15s or are they select-fire military rifles, M-16/M-4? Obama said his civilian force would be as well equipped as the military.
As they are using “sub-machinegun” instructors, I would say they have full auto M4s.
Read their training requirements, it is not about collecting past due taxes, this is combat training, aimed at citizens.
Training syllabus:
https://www.irs.gov/irm/part9/irm_09-002-001.html#d0e613