Thanks for the reply, Mike, but I let me clarify my question.
Let's say that my leader is in contact with 3 artillery units.
The leader's formation is then activated, and he can activate 6 independents.
Do the 3 artillery units have to be activated? Which would then leave 3 other independents he could activate.
Any Artillery in contact count against the activation limits for that formation leader.
In your example, he would only be able to control 3 additional independent units while in contact with 3 artillery units for a total of 6.
So, be sure that you wish to 'pile' on that much artillery on a commander if you think that moving independent ground units on his brigade activation is what might be required in the near future.