".....The upshot was that the baby monitor would have to be nearer to the control panel...."
Baby monitors, ADSL's, automated homes, foil backed plasterboard, the list is endless. We check all these things before installing a trade system. I am thinking of ordering a Yale system to find out what all the fuss is about.
Older Yale's operated at 419MHZ I believe, the next generation at 433 and after that 868. I would suggest that Yale, insert a few paragraphs regarding these potential problems in their literature, but there again we don't see it in trade literature either. These are all narrow band with an insignificant jamming history.
As far as a home "underneath a mast is concerned", I personally would not live there if the house was given to me, and there is as much probability of this mast affecting a wired as there is a wireless system. In some States in the U.S. they have banned house building within a certain distance of power transmission lines and masts. Don't ask me which State or the distance, I read it in Reader's Digest some years ago.