No, most of Europe has their road tax included in the price of fuel, so the more you use the roads the more you pay. So why is it that fuel in all the other EU countries is the same price or cheaper than ours which doesn't have the road tax element added?
The 6 months in any 12 apply if someone has moved here permanently but if they are working here on a fixed term contract, or are a student doing a fixed term course, and have a date in the future when they will return, it doesn't. But yes, it does mean they can ignore speed cameras and parking tickets, just the same as we can if we go abroad.
There were plans a couple of years ago to link all the EU vehicle databases so if you got flashed by a camera in one country they could still trace you back to your home address and demand money. Unfortunately, it seems that the UK data protection laws don't allow DVLA to swap data with their counterparts in other countries......