Even within companies that claim technology as a core strength, familiarity with the actual code and algorithms is rare … one or two steps up the corporate ladder are administrators, not alpha-dog programmers. This will be as true for electronic voting. You need other ways to check, like a control set of machines certified to be running the same software. With that sort of setup, you could create known voting blocks to submit to the machines, and then check their accounting on the other end.