CCA is total crap, it should be banned. End of. It is not category anything, it is wanky cable in the shape/formation of cat5 or similar.
If the baluns say 240m then I'd probably say 250 would be fine, after all ethernet is supposedly 100m end to end max but I have had over twice that on occasions with no issues.
Try it out first off site. To give you the best chance of having no issues then try and allow 1 cam per cable if possible, or maybe 2, 3 is definitely max so you're winding everything up to the limits doing that.
If you are still concerned then use active baluns instead which should give >1km depending on which ones you use.