The Doc's office that did not like competing with my repeater, moved to .575 (another GMRS freq and illegal for them to use) a while back. But, with "their" knowledge of what they were doing, they did not move because of what they could hear, or knowing there was a co-channel user, they moved be because "someone was causing THEM interference on THEIR channel which they could not hear or understand, they just know they were trying to talk and would get covered up, randomly" So they changed to another "channel". They have no clue to are illegal.
Aside from that, now another Doc somewhere about a 1/2 mile down the business strip is using 575 too, but apparently they are both far enough from each other, and on different PL's, they don't walk on each other and don't seem to know each other exist.
Since they moved, I hear them on the scanner, but I haven't done anything else to try to enlighten them, they don't know, and I don't think they care. They figure if they could buy it, it must be legal. Guess I need to go light some fireworks off in their lobby....what? It was legal for me to buy it, so I can use it as I please, right? LOL.
I have never worried about hearing anyone else on a channel I use (I know they are not MY channels) I run PL/DPL and I just do what I want (I do monitor and watch for busy lights). I have never had another legit, licensed user in my area using same channel at same time as me. If I did, and they had a call sign, I would certainly share. I don't channel hog. Now, if you are illegal...I couldn't care less about you.