The topology you speak of here is quite doable with ANT, although depending on your use case this could be quite a bit simpler.
I would recommend reading through at least the opening sections of the "ANT Message Protocol and Usage" document. As in ANT each sensor is a "master" it means that any number of listeners or "slaves" can be listening to the same sensor at the same time.
For example, to enable something close to this use case, AP2 can store up to 3 unique "network keys", but it would be simpler to assign each sensor a different device ID. Each "unit" could then listen to 3 sensors each, and then you could have every station broadcast where the "master" could then open continuous scanning to accept all of the messages from all of the "units". The advantage of this topology I can see is extending wireless range.
But, if each of your sensors did not exceed say 0.5 Hz, a single AP2 is capable of 190Hz of total messaging rate, and 300Hz of over the air coexistence, meaning you would only need one "master" to listen to all 240 sensors simultaneously on the same RF channel.
To tailor a network topology best for your use case it would be very useful to know your sensor's required channel period (ANT sends 8 bytes per message period), distance between "master" to "sensor" and power requirements: do your sensors, units, and "master" run off battery or mains respectively?