Firing the radar into a building only a few meters away from the radome was not recommended on older radars. Even so, old radar systems will have been retrofitted with diodes to prevent large reflected signals damaging the receiver.
Newer radars? Not sure. Although the transmitted signal is much weaker, the receiver may be much more sensitive to compensate for this. However, I'm sure they are an improvement on the older receivers with regards to protection.
The tower radar will be much more powerful than aircraft radar and they haven't been told to turn theirs off on the ground
