Broadcasts don't cross broadcast domains. In the case of a VPN link, each network is its own broadcast domain. Normally you don't want to connect broadcast domains because most networks have way more broadcast traffic than you want to push over a VPN connection. In some cases like this it may be desirable, but it's not possible with IPsec.
http://doc.m0n0.ch/handbook/faq-broadcasts-over-vpn.htmlAs for the OpenVPN part of that, it may or may not get implemented in 1.3. There seems to be some renewed interest, but I'm not sure how far that'll go.