Another way of looking at the bisphenol-A risk.
Estrogen levels in humans have risen significantly, and BPA is a major suspect. Concern? sure. Worry? not too much.

Polyester resins are also not entirely waterproof. What? No really.
They were the bane of boat owners back in the day. (before epoxy owning a boat was once a strong indication of insanity, too much money or both).
What I noticed in my DIY polyester darkroom sinks were pinprick holes that would allow water to seep into the wood swell leaving a bubble, which if not fixed would grow into a worse problem.
Over time you might have this problem in your tomato boxes. More likely you won't even notice it or have a problem with it.

For safety don't microwave in plastic, don't worry about your planter, enjoy your fresh tomatoes--they are anti-angiogenic.

http://www.ted.com/talks/william_li.html

Will