I haven't really noticed as much since the switchover killed the analogue versions of our locals but before that, our locals definitely didn't think much of taking care of their digital signal. It was very obvious they didn't monitor the signal because if something went wrong it would take somebody complaining about it before it would be fixed.
Example: I once noticed that the audio was not transmitting with the signal one evening when flipping through channels and I came across Leno. I didn't bother to call and complain because I wasn't going to watch Leno. The next day just after noon, my wife complained there was no audio when she tried to watch her soap on the same channel. I called and complained and within 5 minutes, the audio was back up.
There are many examples where one of the stations would be stuck in SD (for some reason they have to do this every time they show local commercials or show the local weather) when they should be showing HD programming. Either me or someone else (I saw others in a local Abilene HD forum mention this too) would complain to get them to switch it back to HD.
As far as whether they care or nor for the OTA broadcast in general because most customers get TV via cable/satellite, I don't think that going to make sense... at least not here. At least 3 of the 4 majors networks here are linking to Dishnetwork via the actual OTA broadcast, meaning if the OTA signal breaks so does the Dishnetwork feed (this has happened on numerous occasions). The local cable company does seem to have a direct feed with at least most of them though so they remain uneffected when this happens.