Blank-check companies backed by buyout firm Warburg Pincus and billionaire real estate investor Barry Sternlicht are in talks to take security services firm Allied Universal public in a $20 billion deal, according to a source familiar with the matter. The deal will involve three special purpose acquisition companies (SPACs)—Warburg Pincus Capital Corp. I-A, Warburg Pincus Capital Corp. I-B and an affiliate of Sternlicht’s JAWS Estates Capital LLC.. The SPACs are currently in talks to raise a so-called private investment in public equity (PIPE), said the source, asking not to be identified as the information was private. A representative for Warburg declined to comment, while JAWS Estates did not immediately respond to a Reuters request for comment. Allied Universal’s unique agreement highlights how several SPAC sponsors are trying to come up with new structures and alternative funding sources, as the charm for blank-check deals fade. Dealmaking in the SPAC market has …