The New York Times had a good article about this that came out Yesterday...

“Even with the added show of force from BORTAC, agents will be limited in their abilities compared to the police or sheriff’s deputies. Unlike operations on the border, where BORTAC agents may engage in armed confrontations with drug-smuggling suspects using armored vehicles, immigration agents in cities are enforcing civil infractions rather than criminal ones. They are not allowed to forcibly enter properties in order to make arrests, and the presence of BORTAC agents, while helpful in boosting the number of agents on the ground, may prove most useful for the visual message it sends.”