If you have LOS to the edge of a wood, and a map that tells you roughly how large the wood is and so forth, you should be able to call in artillery on it. It might not be the most accurate - say you're on a level with the edge of the treeline and are dropping behind, you won't know how far behind - but it's doable.
Strict LOS rules for artillery needn't apply, so long as the commander knows that he can get very inaccurate results. Likewise, he can strike very lucky.
I wonder when the Commonwealth module comes out will we see more advanced arty? The British love of set piece, creeping barrages and all that.