They've had problems with certification over the past year. The original plan was to transfer them onto the G-register, but the Russians couldn't agree amongst themselves about who was ultimately responsible for the type their end.
The latest plan, which the CAA have agreed to in principle, is that they transfer onto the Hungarian register, which is full JAR compliant, and where the type is fully certified.
Hopefully, this will end the uncertainty of the last year. They're certainly impressive beasts to fly in, even four-up.
RD