I've read Corbel and ASPA's comments to catch-up contributions final regs. With respect to discretionary employer-provided limits, they interpretted the preamble to mean one of the following: (1) Catch-ups over and above employer-provided limits in an IRS approved plan is ok or (2) employer-provided limits are ok, but not for catch-up purposes. Could the IRS be saying there is no legal basis for employer-provided limits in general?

I have not read the summaries you referenced.

The Treasury has said both verbally and in writing that employer-provided limits done administratively (i.e., not specifically written into the plan) are not in compliance with definitely determinable benefits requirements. Therefore, given that you cannot do them administratively anyway, there is no basis for having catch up contributions keyed off of them (because they shouldn't exist to begin with).

It is their feeling that the only true employer-provided limit is one that is specifically written into the plan document.