You mentioned the foreclosure case opened in April 2008; check to see if the Lis Pendens or Notice of Default when was filed. You'll have to check the foreclosure law in your area (it varies from state to state); typically, the borrower has 6-12 months from the date of the filing to act. If that foreclosure action hasn't been closed, then you'll need to contact the assignee of record to find out about the status of the property. If that assignee owns the entire note to the property, and if s/he is willing to sell (or assign) that note to you, then--assuming the property is still in foreclosure--you'll be able to take over the property when the foreclosure case closes.
Stated another way, an assignment of mortgage is a way for the assignee to invest in real-estate without the headaches of being a landlord. An assignment of mortgage is also a way for the assignor to get cash now in lieu of future payments.
It depends on who the mortage was assigned to. I would certainly double check because you do not want to be paying rent to someone who is not the owner or who will be losing the house.
Lenders, or holders of mortgages or deeds of trust, often assign mortgages or deeds of trust to other lenders, or third parties. When this is done, the assignee (person who received the assignment) steps into the place of the original lender or assignor.