Hrm, I played non-Zero Hour Generals, and I heard something about a general that can pop tunnels wherever he wants in Zero Hour.
Sounded pretty unbalanced (regular tunnels rocked hard enough as it was).
Is that "tunnel spam"?
If so, please give the details. I'm considering buying Zero Hour, and I've been a long time GLA player. I won't get it if this is really a problem though.