If it's a pond, it should've been watertight except for the few drainage holes. Unless your drainage holes lead straight to open yard, or that your pond is buried so that the soil level is above the pond edge, they shouldn't escape. From the runners I've seen, they extend super long rhizomes in a short amount of time, so unless you can make sure they don't make it over the edge of the pond or cut them off yearly, they shouldn't cause much problem. If they get out however, they can spread like crazy.

Bamboo rhizomes (roots) will not "find their way through cement," although they might escape through major cracks. If the pond is intact, there is no issue. In addition, rhizomes are not like tree roots: they seek warmth, so they stay relatively shallow. I've hardly ever found any deeper than 12".

Also, if this is the level of knowledge about the plant world that the second developer has, I'd look elsewhere.

Kudzu is right on the money.. I loathe ignorant landscapers that blindly add to bamboo's stigmatization... As long as the concrete is solid then you're good.. For added security you could adhere some HDPE barrier to the walls to be 110% worry free.. Although it isn't really necessary..

I am trying to grow black bamboo under my cypress trees, but it always dies. Is this a problem with the cypress? Do I have any chance of succeeding?

Beth-
I don't know because I've never lived around cypress trees. But you would have a better chance of getting an answer if you started your own thread.