FAQ answered a couple of questions:
Q. Will you be able to pick what faction you play in MechWarrior® Online™?
A. When you first create your pilot, you are going to have to align yourself with one of the Great Houses in the BattleTech® Universe. Each house will have its benefits and drawbacks and it will be up to you to read up on the house selection menu on which house you will pledge your allegiance.
Q. Will players have the ability to form their own custom clans in MechWarrior® Online™?
A. We're trying to be careful with the naming of some features in MechWarrior® Online™ and "clans" is one of them. Players will be able to form their own customized Mercenary Corporations (Merc Corps for short). These operate in the same way that the term clan refers to in other first person shooters. A better way of thinking about Merc Corps is as a "guild". Within the guild you can create Lances("parties") and join matches in that manner.
Soo ... MERC outfit it is, flying the TOG banner for freedom!
I'm guessing that the story will go "Join great house, become great pilot, bring great shame/decide to strike out on own (or some other great tragedy), join MERC team to repair damage/avenge death/achieve honour"