Medicaid as secondary

So say i have anthem bcbs as primary with a 3k individual deductible. Medicaid pfs as secondary.
Aba Therapy billed with $20 copay for week = $100 but total billed for 25 hours of service would be $1250 i cant remember if this is subject to deductible or not.
So if im only paying the copay would medicaid cover the copay?
And if im actually having to cover 1250 until deductible is met would medicaid cover the 1250? And would that 1250 covered by medicaid count toward my bcbs deductible?
Im asking because my son recieves straight medicaid under the katie beckett waiver. His caseworker told me about another program where medicaid will pay his portion of the premium if i add him to my employer sponsered insurance.
This may help me get him into a better clinic as some of the better ones only accept medicaid as secondary but as im not able to really get any info until next week i was wondering if anyone here knows how that works? Also how this applys to the family OOP max for bcbs. Im going to call anthem next week but honesly never had good luck with their customer service.

Eta ive asked rhis queation before but did not really get any specific answers. Someone repaonded that medicaid would pay what was left after primary was billed but i didnt ask how that pertains to my bcbs oop max and deductibles and woukd it cover copaya.