I disagree, those consultants and lobbyists are working for proprietary vendors. If, instead, public grant money & public purchasing contracts were mandated to go towards free and open source technology, then the nation's technology infrastructure would eventually become free and open. Such a mandate would reduce the opportunity for corrupt contracts in the first place, because it would be substantially more expensive to start a project from scratch if there are already viable solutions in the public domain.
If anything, public money for public code can also dramatically reduce the waste caused by corrupt grants & contracts. If a project falls through, then at least the technology would be in the public domain for another organization to pick-up development. Currently, when a project falls through, it is usually a total loss because the technology remains intellectual property that can not be reused.
Just like with the Linux kernel, if a free and open source solution exists, it can be adapted to meet countless needs with far less effort and cost than starting from scratch with a proprietary solution.