They might use L1's which AFAIK aren't capped.

Almost certainly. Yahoo most likely has a blanket L1: http://www.murthy.com/worker/l-1-visas-statuses/l-1-blanket/

L1 visas are terrible. You cannot change employers on an L1 Visa.

They are better than H1 visas, because your spouse can work. Other benefits: no cap, faster path to green card.

Path to Green Card is long and arduous if its a L1B which is most likely going to be the case

Yes, although H1Bs aren't a great either. Most people I know who were on an L1 got their company to sponsor an H1 visa after a year or two and then change jobs a few years down the switch.

Years before you can change to H1B the next year in US, but lotteries made all these all changed.