An existing cross-tested SH 401(k) plan is sponsored by an affiliated service group. A new group of doctors (part of ASG, only HCEs in that employer) not otherwise sponsoring the plan previously now wishes to sign onto the existing SH and then max-out their contributions for 2007 (calendar year). Can they sign on to the existing plan after Sept 30 and still participate in the SH without needing to separately ADP test?

Sure, if they entered ASG status for the first time during the current year, they can get added to the plan as a result of the 'related group status' becoming effective.

When you said to wanted to max out contributions for 2007, did you mean 2008?