In the Blood Brother mutual war scenario, you may pillage or sabotage an enemy tile without invasion penalty if the enemy tile is touching a tile under BB's cultural control. Diagonal touch counts.
Spreading your corporations to AI cities is fine. If you want to knock yourself out racking up HQ profits, go ahead. The penalty is only for branches in your own cities. You're not responsible for what happens elsewhere in the world.
I considered restrictions, but decided against it. Foreign corp expansion won't rack up major scenario points, like domestic corps will with legendary cities and land from culture border clashes. (Really, that's the only big reason for the corp restriction - too easy to make every city legendary by 2050 AD. 100 corp culture x 2.5 from Free Speech and broadcast tower x 200 turns = 50000.)
Spreading your corporations to AI cities is fine. If you want to knock yourself out racking up HQ profits, go ahead. The penalty is only for branches in your own cities. You're not responsible for what happens elsewhere in the world.
I considered restrictions, but decided against it. Foreign corp expansion won't rack up major scenario points, like domestic corps will with legendary cities and land from culture border clashes. (Really, that's the only big reason for the corp restriction - too easy to make every city legendary by 2050 AD. 100 corp culture x 2.5 from Free Speech and broadcast tower x 200 turns = 50000.)