I believe the MPL system requires cadets to be tied to a specific airline from reasonably early on in the course. (The reduced hours / reduced cost thing only comes by teaching to a specific set of SOPs throughout the course.)
The economy being what it is, I suspect that most airlines are unwilling to commit to hiring cadets in the near future. So MPL courses will be struggling to guarantee places to graduates - which (unlike CPL/IR courses) is a bit of a problem.
Perhaps the MPL will become more popular again during the next up-swing, say 2011.