Since this is a corporation, I don't think number two applies. Therefore, since the corporation is not owned solely by 1 owner and spouse, they don't satisfy #1, and cannot file an EZ. At least IMHO.
A one-participant plan means a retirement plan (that is, a defined benefit pension plan or a defined contribution profit-sharing or money purchase pension plan), other than an Employee Stock Ownership Plan (ESOP), which: 1. Covers only you (or you and your spouse) and you (or you and your spouse) own the entire business (which may be incorporated or unincorporated); or 2. Covers only one or more partners (or partners and their spouses) in a business partnership; and 3. Does not provide benefits for anyone except you (or you and your spouse) or one or more partners (or partners and their spouses).