Not CASS though DOD carriers are supposed to be. They have some work-around on the requirement. Schedules are pretty fluid on a daily basis so reliability is on par with AMC to get where you're going and back.
That said, union hasn't pushed it due to an implicit threat to end home basing if CASS was implemented.
Speaking 2 years time-late (I left in 2008 and there's a new CEO) you are "available" for 20 days a month. Normally was one trip since it's cheaper to stick you in a hotel for a week than to fly you home and back if you have a big break in your schedule.
Actual TAFB varied widely for me. Sat at home for a month + on reserve and never got called. I was sked for a couple trips the but the flight time hogs bounced me from them....wasn't going to break guarantee anyway so I didn't care. In the other extreme, I left for a planned 2 weeks one month and got home 43 days later. I got held on the road and then rolled into next months schedule. Unless you're flying a lot there's really no penalty to the company for holding you out (no overtime unless you break guarantee). Just plan being an indentured servant and expect the company to do whatever is cheaper (1st) an easiest for them (2nd).
Great, great 95% percentile of folks there. The other 5% have skeds on their speed dial and fly anytime/anywhere regardless of the contract to support the company.
Spongebob