Mark: you mentioned that you are going to replace the Polybutylene with copper. I then must assume you are able to solder. If so there are adapter fittings that can be sweated into the tees that will accomodate the poly tubing that is to remain.You will require a crimping tool and rings designed for polybutylene use.
If you opt to use compression fittings instead of copper solder adapters…be sure to use the stiffener inserts in the tubing ends before tightening the fittings in place.
You may wish to install some 1/2″
ball valves on those branch lines just in case a problem arises in the future with the remaining PB.
Here is some info that will help prevent pin hole leaks in your new coppper lines.
Lots of luck…Bud