As far as I know, pretty much anything AI related is server side. As long as you don't screw code up, you can do whatever you want with the bots and it would be server side. This is because the client doesn't keep track with how the bots do what they do, the client only keeps track what they do. The server is doing all the things to make the bots do stuff. Only what they do is actually sent to the client.
You probably can't add gamemodes to maps that didn't have it server side. But you can certainly add bots to gamemodes that didn't have bots and it should be server side. You can probably even add bots to maps that have no bot support in the first place and have it work server side.