Is it permissible to delay the congregational prayer (Iqamat As-Salah) for Dhuhr in the company mosque for one hour, given that the Dhuhr Adhan is at 12:00, and dismissal time is at 1:15?

There is no harm for the workers in the company in delaying the prayer for this duration, as long as they perform it before the time expires. Delaying the prayer within its prescribed time is permissible, and prayer is among the 'extended-time' obligations, which may be performed in any part of its designated time.