Should masts be detectable, in theory yes.
Knowing what I know about the DW engine, I'm glad they aren't, because we can get around this using other AI and player features, and inevitably given the lack of intricacy in the DW radar model, I'm not sure masts would ever be properly detectable...
All I'm saying is, there is far more to be dissappointed about in the stock release than this one specific issue, and far more to be happy about in the modded version of the game... so for me, this issue tends to be somewhat neutral "would be nice, but good it's not done at all than done wrong."
Cheers,
David