I have completed an exterior lighting design that includes both parking lots and streets. A luminiare manufacturer other than what was used in the initial design has been proposed to be used for the project. I have received the .ies files of the proposed luminaires. What is the best way to compare calculation of the initial layout with the results when imputing the alternate luminaires?
It's a bit hard to say without knowing the criteria you're aiming for.
In Australia, what you're describing would typically sound like it falls within what we call Category P lighting, which is essentially local roads and public spaces where Pedestrian requirements are the dominant factor. That means that there are illuminance and uniformity targets to meet, and probably luminaire optical constraints (certain levels of shielding required, or limits on output near or above horizontal angles from the fixture).
If a design is done and a fixture is then proposed to be usable as an alternative in the same layout, it would be just a matter of defining the new luminaires, checking that their optics are acceptable against the requirements of the standard (not always easy, and too often ignored) and replacing them in the existing positions. Assuming the newly proposed luminaires meet the optical requirements and also meet the Light Technical Parameters for the illuminance levels and uniformity in the Standard, the new fixtures are at least technically compliant. There's wouldn't be much reason here to do further calculation comparison, because the new luminaires meet the requirements of the Standard. Whether the original fixtures met the Standard 'better' (e.g. lower power consumption, exceeded the required illumination by 30%, whatever) is largely irrelevant in terms of compliance.
As for assessing any other pertinent information (e.g. fixture quality, features & benefits to the client, cost comparison, etc., that's a larger question.