Am I correct in assuming that a plan can still elect NOT to receive rollovers from another plan, either by a participant or directly from another plan? Or are the EGTRRA rules saying that a plan MUST receive rollovers?

There is no requirment that a qualified plan must accept rollovers from another plan. The only requirement is that a qualified plan must permit a tax free rollover to distributions to another qualified plan, IRA, 403(B) plan or govt 457 plan. While Dc plans can accommodate rollovers easily DB plans do not usually permit rollovers into the plan because it requires that the rollover funds be treated as an individual account and not part of the assets used to fund the accrued benefits under the DB formula.