Management company, owned by 2 individuals, operates two businesses. Mgt co. employees are salaried and are 2 HCEs and 15 NHCEs. The two business it controls are staffed by approximately 50 NHCE hourly employees at a different location.

Can the mgt co. have a 401(k) plan without offering a 401(K) plan to the employees of the two businesses?

Assuming you need to aggregate all three business, yes, if the plan passes the average benefits test. Might have to make a pretty big employer contribution to make it pass, though.

On the other hand, you haven't provided enough information for me to confirm that it is required to aggregate all three.

Are you sure?

If the plan is top heavy then employer will be required to make 3% contribution for non hces in mgt co.