I'm already doing it. I set up cucumber + webrat to run through some quick UI tests. I wrote a mock-object framework into the last feature I designed so I could test it. There's still a huge resistance to change. I'm just hoping I can show how useful it is in the long run. In the short run it just looks like I'm wasting a lot of time tinkering on silly side projects.
Always remember: "It's easier to ask for forgiveness than for permission."
If you want to do better than the cultural norm demands, nothing's keeping you. What's the worst that can happen?