Not that I'm aware of. In fact, I don't quite see a reason for the integration at all since eZ Publish includes a forum system out of the box, including a robust (enterprise-grade) user permissions system.
Unless you're trying to port you user and forum data from vbulletin I don't see any other reason for the interaction between the two systems (actually, there is no real direct interaction, I'm talking merely csv export/import functionality for data and users).
The functionality that eZ Publish may lack with its forum system versus what features vbulletin has, as purely just that, can be easily made up in extending eZ Publish or adding custom information via the templates and content classes.
I am using eZ Publish since 2002 and I am fully aware of it's features. Have you ever used vbulletin?
If you would take a look at the features of vbulletin you would see that it would lasts very long to get all this into eZ Publish.(You can't even write a private message to a forum member in ez publish.).
So, why inventing the wheel again and again and not using a specialist for this case?
By the way: Robert has done a cool forum project here: http://projects.ez.no/xrowforum
And here is a funding suggestion: http://ez.no/developer/open_funding/suggestions_for_new_functionality/ez_community_extension