I replaced the EEPROM on the J282, which solved my earlier problem. 
Trying to boot, I got:

 >> NetBSD/hp700 LIF Boot, Revision 1.1
 >> (fredette@the-gates-of-delirium.home, Sat Jul  6 20:53:40 EDT 2002)
 >> Enter "reset" to reset system.
Boot: [[[lf0a:]netbsd][-a][-c][-d][-s][-v][-q]] :- netbsd
3678208+69632+282624 [427968+101988]=0x4d7810
Start @ 0x200000 [1=0x656000-0x6d7810]...
SPID bits: 0x0, error = -2
WARNING: no HPT support, fine!
panic: no kernel support for PA8000

I guess it is not supported :)
Kirill