in version 1.5 it could be done. Ive just checked pp2 and it seems that when you highlight the group of shots you want to slip they actually slide. If it could be done in 1.5 it must be a bug in pp2
Ive seen in work and tried to crash it, it stood up very well. It can mix various resolutions on the same timeline which is very useful. It can actually do more than the 844/x !!!