What are the chances of that?

I think you would actually be okay either way for the evaluation. The psych may or may not be more familiar with the software, depending on how often he/she uses it, and when the sped math teacher retired. The retiree might have more concrete suggestions about classroom interventions, though. That's what I would want to know, mainly: what he would do, and what kind of outcomes he anticipates. For that reason, he might be a good resource to pull into this meeting, even if the psych does the testing and error analysis.

...pronounced like the long vowel and first letter of the alphabet...