This Green Bin program (don't know the official name) was piloted last year by Bistro and since I went there often to get takeout, I thought it was a great way to save on containers when doing takeout. With the one time $5 fee, you get a card for which you can show (when you order) to request the green bin.
At Bistro you do not reuse the same bin you get, instead when you arrive to order, you simply bring back the one you used last time and you'll get a new one with your meal. If you so desire, you can return the bin early and get a card, which represents you've paid that $5 for the bin for the rest of the year. That's what happens at the end of the year when you leave mac; you return the bin for the card. I imagine it would be similar at Centro:
So my guess is that your used green bin will be returned to wherever you are ordering from, thus then entitling you to another for your next meal or you'll just get the card.
In my opinion, I am glad I am seeing green initiatives like this at mac. It's a simple thing to do. Heck, it would be easier if people brought in their own containers for their takeout. The 25 cents you are subjected to when order taking that isn't in a green bin provides incentive for you to get one and it would probably reduce a ton of waste in the long run.