Is it possible to have pec muscles repaired after bilateral capsulectomy?

If the implants were placed under the muscle, and the muscle was partially released as is most common, then the muscle has probably shortened and retracted over time. In most cases, it would be impossible to restore the muscle to its original form.

This answer greatly depends on whether your implants were placed under or over the muscle 
If under the muscle then yes it is possible to repair the muscle. This is sometimes done by surgeons depending on the intra-op evaluation of the breastpocket/muscle. 
I dont routinely re-insert the muscle back into the rib cage where it was released from but i do suture it back into roughly the same area. Many times these sutures break or release but its worth a try to have things as anatomical as possible plus it tends to help collapse dead space after capsulectomy
Cheers and good luck