Reserves manipulation / other abilites + allies in 7E

I recall a thread on this during 6th, I can't find if it has been answered since 7th dropped.

RAW/RAI can an allied Autarch help with reserves rolls for the primary DE attachment / his own attachment? I know in 6E the RAW was that he could only help a 'primary' detachment.

As a follow up... could a DE Talos benefit from the 3x deep strike that a Corsair Prince (IA 11) confers?

Any thoughts would be welcome.