TimeMachine Keychain backup
All keychain files on the system get backed up to Time Machine.

They are of course each encrypted by different keys for different users so once you restore them, you may or may not be able to get into them as long as you remember the appropriate passwords. Do note that when you reset the password of an account using admin tools (or bringing the keychain to a different OS) - the keychain password is preserved to protect the contents. You really need to use the original password to unlock the files.

I've had no issues backing up Xcode and Xcode server using Time Machine. I would also use the Xcode preferences account pane to explicitly export your developer keys and accounts and store them on USB media and/or burn to DVD and store them offsite in a bank vault/cloud storage/whatever to keep those keys secure and available even if you lose your office due to a flood or fire.