yep. Just make sure than when you frag any shroom that you use really sharp clean stuff, slice through the mouth, so each piece gets a mouth. Quick dip in iodine to make sure they are clean. Set them in a container with some rubble rock, and cover with some bridal veil or mesh screening that you can put back in your tank. The pieces will eventually attached to the rubble after about a week. Take them out, glue them where you want, and enjoy!
If you're not experienced with it, I'd start with cutting in two, rather than 4s or more. Try to do it relatively quickly. the longer you take, the more stressed out the shrooms will be and the less likely they will survive the process.
Here's a youtube video of someone fragging shrooms.
http://www.youtube.com/watch?v=ZtbWJ70oy9M