You can see the new achievements in the global Steam stats for Brink, just not on your individual stats page (until you’ve completed the achievements, then they show up).
For reference, these are the new Steam achievements:
Science Maven
Win Labs as both factions in Campaign Mode
Towering Achievement
Win Founders' Tower as both factions in Campaign Mode
A Burning Thing
Kill an enemy with a Napalm Grenade
Pyromancer
Kill an enemy with a Pyro Mine
Remote Control
Kill an enemy with a UAV
Mutual Support
Have a Field Regen Unit buff more than 3 players simultaneously
Ark King
Reach Level 24