I'd recommend taking normal Pandemic-Proof precautions (glove up and mask up), but otherwise I don't see how this would be truly risky.Whats more, this could be a FANTASTIC opportunity to actually talk to the people inside the homes. 

I support the police in their decision to disarm him pending criminal prosecution and I support the police department's decision to take every precaution to protect their officers.

Generally need separate entrances, utilities, egress windows, and all the same safety precautions for each unit.  

They charge those fees simply because they can.The risk is that, despite all the precautions, the second closing doesn't happen.

What precautions should be taken?

Same if you say have a broken stop valve inside and you have to cut the pipe to replace the valve or run the water through the tub/shower valve to the shower head.Do you take any extra precautions when flushing the system out initially, if so care to share what you do?

If so, did you only treat the one unit and hope they didn't spread to any others, or did you take precautions on the adjoining units?

Lead is nothing if you take proper precautions.

What are some precautions and preemptive measure I should consider?

It's likely true that there was no intent to defraud, but if the institutions are acting with gross negligence (not taking reasonable precautions to protect consumers), they are still guilty of criminal behavior.