In Estes Express Lines, Inc. v. U. S., No. 11-597C, January 15, 2013, the Court of Federal Claims said:
"For the government to be sued on a contract pursuant to the Tucker Act, there must be privity of contract between the plaintiff and the United States." "This is so because the doctrine of sovereign immunity precludes a suit against the United States without its consent and because, under the Tucker Act, the United States has 'consent[ed] to be sued only by those with whom it has privity of contract."' Accordingly, "[t]he effect of finding privity of contract between a party and the United States is to find a waiver of sovereign immunity."
Conversely, a finding of lack of privity deprives this court of jurisdiction.
See the opinion here.