Unless things have changed, I am afraid the 6000s are totally incompatible with the 1 or 2 and the PSTN base.
But I'm here in the States so the EU may have better luck. Again I think that when B & O released the 1 (to replace the 6000s), they took away backwards compatibility for the 6000 as well as it's forward compatibility.
A great way for the company to snatch more profits from loyal customers who want to upgrade... need to replace the entire phone system.
Love B&O, but no longer addicted.