As someone who's played Law Enforcement on a WoD MU before, here's my take on things.
I don't give a fuck about what the majority of Crime PCs do on the grid. You want to be a drug dealer, or have your little den of sin, who the fuck cares. The issue of PC vs PC arises (at least for me) when someone does something monumentally stupid as fuck. Like if you decide you want to open fire in the middle of the street, I see no reason why Police PCs can't open fire right back. Aside from that, I have little issue with people getting busted for possession and then let go the next day or something like that being hand-waved. It creates RP, it creates contacts and relationships between characters.
That being said, some sort of Metro Task Force would be a good way of going about things and probably makes sense given the state of things post-9/11. I would also suggest making Law Enforcement Mortal only. Nothing sucks more monkey dick as a detective than Mages coming in and rolling all sorts of dice to "solve" the case in a handful of turns. And I say this as someone who genuinely likes Mage.