I have a 401(k) plan with deferrals only, no match, no P/S contributions. The company owns a number of different entities and we recently established that a control group exists with 3 other companies. 2 of the companies have employees and offer a Simple Plan to approximately 30 participants. What will need to happen as far as including these companies with the 401(k) qualified plan? Do they have to be included under the plan, what about testing?

I'd be curious to see how this will turn out. you can't have a SIMPLE once an employer goes above 100 employees, and I can't tell from your notes how many total ees there are.
If you can pass coverage without aggregating, then of course you run the ADP test separate. If you aggregate for coverage, then you would have to aggregate for ADP test, so I assume, despite the fact a plan might be SIMPLE, the numbers still show up on the test. (That wouldn't be much different than a safe harbor plan that failed to give timely notice - despite the fact a safe harbor contribution was made, it is still tested) I would think same logic applies.

Are the SIMPLE plans SIMPLE IRA's or SIMPLE 401k's? If they are SIMPLE IRA's you may have another problem. A SIMPLE IRA must benefit all members of the controlled group. If it doesn't benefit all members, the SIMPLE generally isn't valid.

You may have a similar issue with a SIMPLE 401(k). I don't know that much about SIMPLE 401(k)'s. The exclusive plan rule still applies, but I am fairly certain you can exclude people under a SIMPLE 401(k), so maybe with exclusions there is a way around the exclusive plan rule. Again I don't know.