We've upfit one or two at work. Yes the deal with Toyota is true, they are now affiliated with Toyota, however the support was not through Toyota, still ran through Hino at that time (about 8 moths ago).
Don't know what the durability is going to be, but I know the axle capacities were quite a bit lower than IH and the former GMC 5500 series.
BTW the chassis we worked with were not the cab over's you normally see, they were a more traditional chassis with the tilt hood and such.
Don't know where your boss is looking for a chassis, but I know the purchasing group at work has been getting killer deals in Ga. on Peterbilts. Sweet rides, optioned out for less than a run of the mill International.
I should have some tech. info, upfitter & body builder stuff still around if you need any more info.