I work in a large defense company command and control and intelligence systems and we were charged with working with DHS to see if we could apply our products to any of their programs. We found that there are a few large procurements but the vast majority of their funds seems to be keeping their front line organizations going (USCG, TSA) and paying small amounts out to cities and municipalities everywhere. There were a few big DOD style acquisitions like SBInet (virtual border fence) but even those tended to fizzle out after a couple of years, never reaching the talked about contract values. Most of their acquisition money went to small business science projects and to grants. To be fair, some of the grants were fairly sizable and were for system, not just gear (cameras, port security, etc). Still localized and through grants.
Anyway that was our experience.