Can new construction recessed lights be installed in inaccessible ceilings?
Yes -- the junction box of the recessed light must be accessible after installation per the design of the recessed light. The typical design I have seen to accomplish this is that the recessed light's "can" is attached to the recessed light's junction box by flexible cable. The "can" may then be pulled down after installation through the opening in the drywall to allow access to the junction box.

Here are some before and after pictures of a new construction recessed light I have left over from my remodel.