It won't break the module, though certain things probably won't show up ((placeables)) correctly. You may run into scripting problems, for example, if some placeable ((a portal for example)) is spawned in via some action, ((like pulling a lever)) where 2.4a has changed that placeable 2da line to be a tree, or whatever.
As a heads up, 2.4a is not as bug free as 1.5. The new team has left quality for quantity, and some things that are in it cause crashes, and/or missing parts. There is a forum for the CEP2 team, where you can post any questions/ comments to the CEP2 team.
http://nwncep.forumotion.com/forum good luck!