Corporation A is "administratively dissolved" and has been so for several years. To "reverse" Corporation A's dissolution, by one attorney's opinion, would require paying some 15 years of annual filing fees and minimum excise taxes.

May Corporation A transfer its real estate assets (and corresponding liabilities) to Corporation B with out "reversing" the dissolution?

Both corporate entities have the same sole owner. Corporation B has been paying all property and other taxes as due on the Corporation A land. Although the mortgage has been in technical default for many years (the mortgage holder is deceased), the (unknown) successors to that interest have not made any effort to intiate foreclosure (perhaps due to the potential liabilities in the legal, permitted and ongoing use of that property as a disposal site).

If such a transfer were effected, is the mortgage obligation (against the Corporation A's property) limited to the specific land so encumbered, or does Corporation B become liable for any obligations in excess of the liquidated value of Corporation A's orginal parcel of real estate

This is a complicated issue. I would suggest that you speak with an attorney so that you make sure if this is legal and that all paperwork is in order. You can locate an attorney through the attorney locator on Lawinfo's home page at http://www.lawinfo.com/. Some do offer free consultations.