This quick little piece from CIO has seven quick reasons why telecommuting is good for business. The information is good fodder for your telecommuting proposal, because most of the pros are from the employer's perspective. One that I think will particularly get their attention: "Telecommuting means no excuses for missing deadlines."
I like this because it's absolutely true. I am one of a small collection of full time remote workers in my organization right now, and I keep (informally) lobbying my Real Office colleagues to exercise their ability to work from home for their own purposes. It's a hard-charging environment and there are no excuses for not working until the job is done.
But the fact is that people who know how to use tools can work wherever they are, including home. So they should do so.