I would expect a few at a time. The reason you see flight attendants and pilots being recalled in blocks is because they have to be re-qual'd, and it doesn't make sense to ramp up the training center for just one class. For the other workgroups, it's typically just a matter of finding someone who can step in and do OJT, or using full-time/part-time instructors who are already carved out of the manning to do recurrent training.
I seriously doubt that there would be buyouts. The rationale used in 2003 was that they cost way too much, and furloughing was cheaper.
It's a heartless way of looking at this, but what motivation does management have to bring back furloughees aside from being able to issue a press release?
Equally heartless, what benefit is there for the TWU to push for this, aside from lowering the overall dues base (assuming they're still based on hourly wage, right?)?
WN is offering them, but they're not bringing back furloughees -- they're hiring replacements off the street (and that assumes they're replacing them on a one for one basis). They've got a totally different retirement plan; when their employees retire early, they have their 401K, and management gets to wash their hands of any future obligation aside from pass travel.
When AMR employees retire early under a buyout, pension fund payments replace payroll (albeit at a lower monthly rate). More people drawing a pension than forecast means the fund probably has to be topped off sooner than it would have otherwise.