I left a beer in a polycarbonate water bottle for over a year when I moved to college years ago. It was in my parents basement and I forgot about it. Anyway about 16 months later we bottled it and there was no indications of oxidation.
Polypropylene (white) carboys are used by many for aging beer and wine and is more permeable than PC. You'll never beat glass or SS, but sometimes the levels of O2 permeability we are talking about are extremely low, so I sometimes wonder how much a concern this really be.
The brewing industry was looking into ABS plastic for fermentors and cold storage tanks but decided the cost was still to high to replace SS.