The Kaiser Bus (and there was more than one built) was a contract job between Kaiser Engineers and the Santa Fe Railroad. Like other western train lines, Santa Fe used busses to connect various areas rather than run regular train service between the cities. Busses were cheaper to operate on the low volume lines. They went into service during 1946-47.
As far as is known, all the busses were scrapped during the 1950's. Their heavy % content of magnesium helped enhance their salvage value.
If anyone is interested, I suggest they contact BNSF for any additional info their historical archives may hve.