Quote Originally Posted by yesdachi
EYG, have you had any experiences where you get a spy in an enemy province before they build a BF and leave them there? Or a province that was yours and was taken over by an enemy? Doesn’t the BF only stop/attempt to kill spies and assassins when they enter?
If a spy enters a province without a border fort, and later the BF is built he will have the normal chance of getting killed. I've lost 5-star spies that way. When I checked the following year, the AI had built a border fort.

I know this doesn't directly answer your second question, but it reminded me of a couple of instances where I've lost a spy in a province with a BF that I had just taken over that turn. For example, in the same year, I sent a spy and an invading army to, say, Constantinople which had a BF. After ending the year and winning the battle I received a message telling me that my spy had been caught by enemy bodyguards.