Can I keg my homemade soda?

Absolutely. You can even force carbonate it. If you are kegging your soda, you can just make the soda right in the keg, omitting the champagne yeast, and force carbonate it just as you would with beer. It is a good idea to dedicate a keg to soda making since the flavors can get trapped in the O-rings, or simply change out your O-rings when refilling the keg with beer.