The letter doesn't explicitly say (I'll way to hear from friends at CRM to get actual details) but their SEC filing mentions stock-based compensation as an associated cost of the layoffs, so it sounds like accelerated vesting might be happening.
I read that they will technically be on payroll until late March. If that's the case, it's not so much accelerated vesting as it is vesting while not being "employed".
FWIW, I was laid off earlier in the year, and was put on garden leave for 60 days. My vesting stopped immediately, even though I was still employed for 2 months.