I would try a product to either slow down the root intrusion, or have the piping lined.
http://www.rootx.com
Try a search on the major search engines under “pipe liners”.
Sorry it took a year and a half for you to get a reply, I am sure the piping problem was resolved, grass and trees are probably growing with no sign of work ever done.
“Your best interest is secured by making the right decisions the first time.”