Mobile is interesting, because while the kernel is theoretically GPL you can't normally replace it with your own kernel without using a security exploit against your own device to get root. And almost all the userland is closed as well. It's far harder to run a properly Free operating system on a phone that nominally already runs Linux than it is to install Linux on a PC shipped with Windows.
On mobile, Linux is a thin shim of Free software in a proprietary stack.
Publicly traded companies are required to disclose revenue, but not required to break it down by source.
Neither Apple or Google break out the revenue from the *Stores (unless they have started doing it very recently). There are third party analytics firms that provide reasonable estimates though[1].
Are all companies which have such stores traded publicly? I don't see a direct connection between these two aspects. For instance, in China there are various Android markets and I'm not sure all of them belong to publicly traded companies.
Because Linux does dominate mobile? Android is Linux and iOS is a *nux. (iOS is a BSD derivative.)