401K plan for non-profit via multiple employer plan

[Benefits 101]

Same situation as this fine article:

http://benefitslink.com/modperl/qa.cgi?db=...esign&id=11

However, the "spin off company" is a 501©3. Can they co-sponsor the 401K or the controlling organization?

This isn't my area of expertise, so pardon if this is a stupid question.