Depends. If you are a contractor, like most craftspeople, your tools are your own.
Some agencies do, however; it's dependent on the contract specifics.
When I'm hired in a company (not contract), they wipe the harddrive when I leave (well, I also do it before I hand it over sometimes). So they don't get the tools (I take them with myself, it would be a waste to loose them)
As per NDAs and work contracts, nothing is supposed to leave either employer nor customer systems into unauthorised third parties.