I think this thread really has all the info you need:
If you want to use the modular certification from ublox, you must use an antenna with gain equal to or less than the antenna that was used for testing (as specified in that thread) in any band. Basically your radiated power should never exceed the original test and you are fine for the intentional radiator testing, as long as you are not building a close-to-the-human-body device.
You still need to do unintentional radiator testing on your final product but that can be done with the cellular radio off.
If you are building a product and want to use the modular certification, I suggest that you contact Particle sales via email and talk directly to them about your needs.