Yes, realistically. But, realistically, the police never would have allowed the armed robbery to happen in the first place.
Mr. Orange would be culpable for the murders of the tellers and cops (not to mention the pregnant woman he shot while doing GTA).

Yes, having re-watched part of the movie via netflix, the cops have the place surrounded and the two cops in the warehouse (the kidnappee and Mr. Orange) discuss it after Mr. Orange kills Mr. Blonde.

Orange would've told them where they were going to meet after the robbery. They would've had officers waiting. As orange said, they would be waiting for Joe Cabot.

I'm not sure the cops had the warehouse surrounded. I suspect they showed up later, and got there as Mr. Pink was leaving with the diamonds, or perhaps just before then.

Same reason they didn't interfere when a policeman was dragged out of the car after being shot in the gut. They were told to wait for Joe.
As for Joe, I just chalk up to him being so heated he wasn't thinking straight.
Seize the moment, 'cause tomorrow you might be dead.