@Papethova: You can just get this type of temporary plates in Germany, since the car will be moved out and just has temporary homologation. As I understand the regularities of the ring, all types of temporary plates are excluded.
@Dackelone: They explicit mention the export plates as forbidden.
"Fahrzeuge mit Überführungs-Kennzeichen (rote Nummern), Kurzzeitkennzeichen (03er- und 04er-Nummern), Oldtimer-Wechselkennzeichen (07er-Nummern) sind nicht zugelassen."
Just found the english version of the ring-rules:
"6) Vehicles with delivery number plates (red numbers), short numbe rplates (03 and 04 numbers) and vintage car exchange number plates (07 numbers) shall not be allowed."
http://www.nuerburgring.de/fileadmin...uristen_GB.pdf
I don't know. Perhaps the guys from Canada didn't get their plates checked or there was another reason they got on the track. But looks to me that it could happen that you aren't to go on the ring?
I would definitely check that. Perhaps they say it's ok, I don't know.
Edit: Or perhaps the Export-plates are not forbidden. But there are different kinds of plates, it's a little bit complicated.