Just for reading the summary I can say this looks fishy. The latest Anroid release 4.4 was mainly dedicated to make Android run on smaller devices, adding tools to debug memory footprint, adding compresion of pages, sharing of things, etc. Google claims that now Android can run on a 512 MB device (which is fairly low end right now). And with ever decreasing memory prices is hard to imagine there's a place for a "lower than lower end" OS.
The "being open" reason is also not good enough. As a technology (i.e. removing Google services) Android is 100% free software. And the reason some telcos might want Firefox OS is to have a more closed environment which they can control.
Maybe Firefox could have been working to create its own Android fork, replacing Google service with Firefox services. That would be, IMO, much cooler.