I have read a ridiculous amount of omegaverse and haven't come across that. I've seen alpha x alpha, alpha x beta, beta x beta, beta x omega but never just omega x omega. On anime planet there's a list of nontraditional omegaverse pairings and there's a few on there I haven't read(but plan too ASAP). If you're into novels there's a series by Rosa Swann called "Omegas' Destined Alpha" there's approx 8 books in the series and it features a throuple consisting of an alpha x omega x omega that are fated mates. It's very good if you're into this genre and like to read novels as well I highly recommend it.
Rotten To The Core