Top-paid group determination and acquisitions

[Guest NiceGuyMike]

I have a plan which utilizes a top-paid group election. At the beginning of 2003, they acquired another company (I don't know yet whether by stock or asset acquisition). The existing plan recognizes prior service with that employer (and prior service for pharmacists from other employers) for eligibility, vesting and contributions. What I'm not sure of is whether their prior service should be counted for purposes of determining the number and composition of the top-paid group.