I think these are designed to be impervious to
roots from the biosphere above. I once lived on the banks of the Los Angeles river (not as scenic as it sounds), and no plants seemed to be able to establish themselves in the concrete of the channel. Drainage channels aren't even a good place for plants to look for
water, because half the year, the channel is bone dry. Roots would probably do better expanding
under the concrete of the channel, since any porosity to the bottom of the channel will make those places sources of water. I know in Albuquerque, they can get a good crop of tumbleweeds in the drainage channels, but those are annuals that quickly go to seed and dry out when the moisture is gone.
If you intend to garden with raised or
hugel beds, it's probably not going to make any difference.