For example, if you wind up hiring a Linux guy, he'll implement all sorts of solutions for you based around that operating system. The same goes for folks who advocate Windows or Mac.
The point? It's a good idea to take stock of what your company has invested heavily in and to find out whether the consultant is well versed in that technology. If not, you might have to make more costly changes than you had in mind to solve problems that may have been handled well with at least some of what you already had.