I've been that "only Lisp guy" and had good success mentoring small teams (say 8) to Lisp profiency. Any good development team will have a star or two who get it really fast and help mentor the others. Both times I've tried this it worked, and both times one of the main advantages was the excitement that developed on the teams.

It's not so much about learning Lisp as about what happens to you while you're learning Lisp. There are companies out there that understand the value of having a team of developers gel and produce the best work of their careers. Hard to quantify this for management though, you really need to have their trust.

For me Lisp blurs the line between science and art, it is a work of genius that transcends both. It places very minimal barriers between your designs and their implementation. Once you are conversant it becomes unconcious; it is akin to a musician becoming accomplished at their instrument. With the lack of concious effort they feel the music more than play it. Any skilled painter can also relate.

GUI's like Emacs and SLIME facilitate reaching this Zen state. Keyboard based commands become ingrained in muscle memory and the developer is free to focus on the patterns and frameworks of their design. The process feeds back on itself and the result is truely enlightening. These people aren't writing code, they're producing art.