Here is a very complete discussion of the issue.
in part it states:
The physical interchangeability is not an indication that they are electrically interchangeable. This must be verified by test. Unless the circuit breaker is marked on the panelboard as being acceptable or it is Classified as being acceptable, the circuit breakers have not been tested in the panelboards and should not be used…
The Classified circuit breaker must be marked to clarify the limitations of use on short circuit applications and series ratings. In addition each breaker is required to have a Compatibility List which, according to the UL Listing Card for Classified circuit breakers, “… tabulates the company name, catalog number, number of poles and electrical rating of the Classified circuit breaker, in addition to the company name and catalog number of the applicable UL Listed panelboards,
What about the requirements of 110-3(b) of the National Electrical Code? This Code Section requires that products be used in accordance with instructions included in their listing and labeling and the use of Classified circuit breakers does present a dilemma to some inspectors.
The panelboard is marked to indicate the only circuit breakers to be used in the panelboard are the specific Listed circuit breakers with which the panelboards were evaluated and Listed by the panelboard manufacturer. The Classified circuit breakers, on the other hand, also have instructions included in their listing and labeling indicating the specific Listed panelboards for which they have been evaluated for use in. These are not in conflict with each other. Each manufacturer is listing and marking in accordance with the testing they have done. The Classified circuit breaker manufacturer has done testing in addition to the testing done by the panelboard manufacturer.
The final decision on acceptance of Classified circuit breakers, as with any issue, rests with the Authority Having Jurisdiction (AHJ).