No, on DirecTV recordings are tied to the receiver ID number (along with programming authorization from the access card number).
Moving a hard drive (external or even internal) to another DirecTV receiver (regardless of model - even if the same) will not have any playable content. The recordings will show in the list, but will be unplayable.
I've never read of anyone being able to keep recordings from a dead or retired receiver, no work around.
There are ways to copy recordings off a failing hard drive, but they would still only plan in the same receiver they were recorded from.
Eventually - the right fix for this would be to tie recordings to the account instead of the receiver, which would leave an external drive playable if a DVR dies and is replaced. I imagine this is a content provider issue because there hasn't even been a hint of anything like that ever happening.