Having said that I think drathe's comment is probably the most accurate and have voted 'No, they are two different worlds, and that's that. Any similarities are due to the fact that the same people created the backgrounds and re-used some ideas.' to reflect that opinion.
drathe wrote:It's my belief that Games Workshop chose to use the Warhammer background as it was already developed. HeroQuest would be a great way to draw new players into their world (and other games) as it would already be familiar to them.
However, would it be possible to consider them the same world but at a different time? e.g. HQ = WH + 100 years.
This could explain why Mentor/Loretome are not mentioned in Warhammer and why some of the places in HQ don't appear on the WH map (I think this is mentioned in another topic on this subject)