Legally speaking, the employer’s need to monitor the workplace generally takes precedence over employees’ claims to privacy. This is the case in large part because of the fact that employees know that they are at work and that they are liable to be monitored.
When people go to work, they understand that they are going into a public place. They also understand that their actions can have serious impacts on the financial health of their employer’s firm. For these reasons, they should understand that they are giving up their right to privacy. Their employer has the right to monitor them via video (except in places, such as bathrooms, where they would reasonably expect privacy) to make sure they are not, for example, stealing. Their employer has the right to monitor phone and email communications to ensure that they are not doing inordinate amounts of personal business on company time. Their employer generally has the right to test them for drugs to ensure that the employer is getting the most out of the employees and to guard against employees harming others while affected by drugs.
Because their actions impact their employer, and because the workplace is a public place, employee claims of privacy are generally trumped by employers’ needs to monitor the employees.