Just because they can be summoned, doesn’t mean every one you run into has been. They exist outside of being conjured. That said, I think if it has been conjured, no it cannot give consent until the spell wears off. If I recall correctly, even if you hit them, they won’t attack you while summoned. I’d say that is a pretty clear indication that they cannot decide for themselves while under the effects of the spell.

But that doesn’t mean you can’t find one out in the wilds and “befriend” it the old fashioned way, without magic, in which case yes, it likely has the intelligence and autonomy to consent. Which really makes the spell to conjure them pretty fucked up in itself…