If not, then you probably won't have a leg to stand if legal action is taken. If you read the terms of the sunrise registration closely, you would probably remember that there was a window for Trademark holders to register their .mobi domains in cases where a company name is trademarked, etc... If the name indeed is trademarked, I seriously doubt that the company is 'required' to register the domain name during the pre-reg for trademark holders and/or sunrise period pre-reg for everyone.
Either way, if your intention was to hold the domain for ransom in an attempt to make a quick buck, then you'd better be ready to play the legal game with the big boys. If not, sorry for jumping to conclusions. This has happened with several Google domain names (not necessarily .mobi) and the end result is that big G won the suit. If the name is trademarked, give it up to them at reasonable cost to cover your expenses and watch your step closely when doing things such as this in the future.
What should I do if they go for legal action?
If you've let it get that far, you have two simple options.
1. Hire the best legal team in the country. This will require a new mortgage, selling the kids, and the 10 million you stashed under the bed.
OR
2. Leave the country. Forever. They'll still have the hearing, they'll still win, and your debts will happily await your return.
What were you thinking when you bought it?
What were you thinking when you refused to give it up?
The last time anyone made a profit / escaped bankrupty in such cases was 1998 :)
Good Luck.