there isn't as much exotic "stuff" as you might think. they have the same ODMs build switches and line cards to their specifications, with chips from the same vendors (Broadcom, Cavium, etc) only they can easily hire a team and sign the NDA and write/optimize/perfect the forwarding plane and control plane implementations.
hell, the IS-IS implementation in Quagga is usable because of Google :)
hell, the IS-IS implementation in Quagga is usable because of Google :)