So the rule regarding PD Raids pretty clearly states that you can't advert a raid while inside the PD, because it's essentially failRP to stand among a group of people then randomly whip out a weapon and massacre everyone. It's assumed you're going to kill everyone in the PD when you raid it.
As someone who loves the undercover jobs and operations I have a question regarding the specificity of this. Let's say you, some class of thief/raider, make your way into the PD and pose as an inmate for a while before a raid. Would it be FailRP or against any particular rules to wait for your raiding group to begin the raid, advert an "assist", and join them from inside the jail cells?