I honestly don't remember. I know the idea of hosting a contest with both infs and cavs has been brought several times in the past but I don't know if it has actually been pursued by an actual event.
If we speak about group fighting format, obviously there was
Marxeil's recent tournament but when it comes to having an actual league with both infantry and cav regiments being teamed-up to compete against other teams of both cavalry and infantry regiments, there is nothing coming to my memory.
But said memory being what it is, it wouldn't surprise me if such contest had actually taken place and I just can't remember it because I didn't play it.