I noticed that as the aedui, when I took the west-most gallic city, the one where you have veneti baguadas to train, it says that you need a type 2 expansion government to train them but you can only build type 1,3 or 4 in that province. so in other words they are unusable in campaign since its the only place you can get them.

sorry i cant remember the name of the province d-_-b