Molten-WoW has taken a step further than any other private server has, and is working to implement cross-realm battlegrounds.
Here is an update on what’s been happening lately.
Cross-Realm battleground development
We started working on this about 1.5 months ago and it’s still in early development. This is the single most complex and challenging feature we had ever undertaken but we started on it. We don’t exclude a possibility that at one point we will stumble upon some issue which will make this impossible for us due to limitations in infrastructure, manpower or even expertise, but current realms are already running with some of the major internal structural changes required to make this long-term goal possible. Current estimation is 2-4 months.