Multiemployer Plan?

[Guest erisa15]

Company A currently sponsors a profit sharing plan for 15 wholly owned subsidiaries. Company A is now looking to buy another 10 companies. Company A may buy these new companies with Company B with each owning 50% of the new companies. Since Company A already sponsors a profit sharing plan, can the new companies participate in Company A's plan without creating a multiple employer plan situation? (I think we will create a multiple employer situation). The other option would be to have Company A buy all the new companies, manage all the companies and then pay B a fee. Thoughts?