Is it permissible for an employee to pray in the mosque near his workplace if the company prevents him from doing so, claiming the presence of a prayer room, and threatens to deduct a portion of his salary for spending prayer time outside the company?

Praying in a mosque where the call to prayer (adhan) is made is better than praying in a musalla (prayer room), due to the hadith of Ibn Mas'ud: "Whoever wishes to meet Allah tomorrow as a Muslim, let him observe the prayers wherever the call for them is made." It is permissible to pray in congregation in a musalla prepared for that purpose by a company, and one will earn the reward of congregational prayer, provided that the imam is one who observes the obligatory tranquility.