Quote Originally Posted by EatYerGreens
Get an emissary or bishop into the province and check to see if it has border forts or not.

At least in Shogun, as soon as a neighbouring enemy province put up BF's, your watchtowers stopped providing information about buildings and army stack contents. You could still read the province parchment (income, faith, loyalty) though. The BF's basically act as counterspy, stopping certain info getting out and you may be seeing a similar effect.

Strangely, in MTW, BF's in a neighbouring province don't block your watch towers at all. Perhaps ships are being treated as a lesser quality of agent?
That's a very good suggestion indeed!