According to the linked table, it's monazite which is no longer processed with sulfuric, not bastnaesite. Nonetheless, it can be done.
I suspect the chloralkali regeneration is very helpful at Mt. Pass given the limited water resources. Very challenging acid-base environment that must have required new materials, new steels, etc. Damn shame that they went under.
The linked source also provides some information on apatite (AP) processing.
http://www.eurare.eu/docs/eres2014/seventhSession/SebastiaanPeelman.pdf
p.s. I should have included Sm in the list of magnet metals the Chinese are undoubtedly interested in from Mt. Pass.