Motorola and its affiliated entities are notably absent

I would agree with you that evidence is required for MPEG LA to collect royalties. The statement their spokesman made to The H Online suggests they're working on just that.

I said "highly unlikely" because the realm of codecs is a terrible patent thicket. Also, in terms of credibility, Google originally claimed that its own patents were sufficient and now presents a 17-member pool, which is in and of itself already a bit inconsistent with the original claim.