It’s possible, but the APIs (you are requested) are authed. Same as the subscriber API of Twitch is authed. You need to be following. Unless you find a way to get passed that, I suggest you also ask this in (for example) a ticket to the actual LoL community/developers and not here at Twitch.
How come you thought the LoL API would be integrated with Twitch API, btw? I’m quite curious now.