To be clear, "getting caught" means you get an automatic ban from the realm that owns the region, but you are not imprisoned.
Also, it would be deeply pointless to try this on a rogue region.
If you lack ambassadors and the rogue city in question doesn't have enough sympathy to your realm for you to do the CTO you want, it would be useful to fund the rebels there, assuming it's even possible when the region is rogue.
Unless I remember really poorly, the action increase sympathy quite a bit.
Mind you, should be much cheaper and easier to find a diplomat though.
