Hi. Oldish post but I have a very relevant reply !
No. At the moment its not possible to call in artillery strikes unless you are ...
1. The commander.
2. You are in Coop and your friend is in the commander position.
The AI part of artillery/supplies got broken in the BF2 1.5 patch. It's a mystery to me why DICE/EA never acknowledged the fact or patched it but whatever.
The problem with No. 1 is that you have to be sat at the commander position (chair or commander vehicle). In 1 player Coop there are no other human players to call in artillery. However the is a python script alteration that was posted on the forum somewhere that free's you from having to sit at a position (I have it somewhere, available on request).
There is now a python plugin that can add artillery/supplies which I've tested but it needs some tweaking and testing before adding to something like Forgotten Hope -
https://www.moddb.com/games/battlefield-2/addons/advanced-ai-commander-plugin
