Including in your post the language "fair, reasonable, and non-discriminatory" implies that you think that FRAND has something to do with this. It does not. FRAND is reserved only for standards essential patents, and standards essential patents only come into play when standards bodies get together to create standards that 100% of products in a category must comply with to be compatible (i.e. standards like USB, SATA, h.264, LTE, HDMI, ATSC, etc.) Patents must have been voluntarily submitted to the standards making organization to become FRAND, patents can't be made FRAND against the will of the owner.
If among the patents Microsoft owns is ExFAT, that is not covered by FRAND because it is NOT a standard. It is a Microsoft owned technology that became prevalent in the market because Windows PCs can read it. There's no requirement that phones support ExFAT, and smartphones can be produced that are still smartphones that do not support ExFAT.
Even if Android owned 99.9% of the market, if there were MS patents infringed by Android they would not be FRAND and Microsoft would be under no obligation to license them to anyone at all, let alone on equal terms. They would be within their rights to charge Samsung $30 a handset, and HTC $0.30 a handset if they so chose, or to make per handset price contingent on selling a certain percentage of Windows Phone handsets (at least so long as Windows Phone didn't approach a monopoly share of the market, which doesn't appear too likely)