I will remove the references to the bburl in 1.1.0, but you really should not have any problems there UNLESS AdminCP -> vBulletin Options -> Site Name / URL / Contact Details -> Forum URL is NOT set to your forum base directory and is instead set to your webserver root.
I'm pretty sure bb-codes weren't originally designed to do that. Doing what you suggest with a tag (overriding a vbulletin setting) may prove impossible without serious file edits, unless it was the tag itself that acted as a setting.