It's all about Linux. IBM's running Power8 with RedHat in SoftLayer data centers. Hadoop and jboss are some of the target workloads.
At the same time, if they are "using it behind the scenes", yet not offering it to customers, that would be very bad for brand image. Isn't the crux of the selling points server consolidation? Which of course is the same exact thing "cloud provider".
I still haven't tried it, but siteox.com has it though.