All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
We have already clarified in Fatwa 82264 that men are obliged to perform obligatory prayers in the mosque.
As regards the amount of time permitted for the workers to perform the prayer, then the jurists clarified in the chapters of hiring in the books of Fiqh that the hired person has the right to take time from his work, which should be enough for performing ablution and the obligatory prayers and the supererogatory prayers related to them, and the Friday and 'Eed prayers. The employer should not deduct from the workers' salary the time during which they went to the prayer, as they are allowed to do so by religious texts.
The jurists also stated that the employer is not obliged to allow the workers to go to the mosque unless it is near.
Therefore, if the situation is as mentioned in the question that the mosque is 15 minutes far by car, then this is a far distance and the employees are not obliged to perform congregational prayers in that mosque. In this case the employer has the right to prevent them from going as they are not religiously obliged to go. Indeed, they may perform the prayer in congregation at the work place and they have the right to take time for ablution and the obligatory and supererogatory prayers.