Can I use RTAS plug-ins with my Mbox or 002 in DP 4?
RTAS plug-ins are available only under DAE, and DAE is only for TDM (Mix or HD) hardware.
Since outside of Pro Tools you must use LE hardware with a CoreAudio driver, you don't have access to DAE with an Mbox or 002meaning you can't use RTAS plug-ins.
For more info on using RTAS plug-ins under DAE in DP 4.5, check out the tech note, How do I use RTAS plug-ins in Digital Performer?.