May employers collect current private mobile phone numbers or other contact details from employees in order to be able to warn or urge employees to stay at home in the event of a plant closure or similar cases at short notice?
For corona prevention, many (professional) associations recommend setting up an "internal communication network" tailored to the respective company, so that companies can take certain measures depending on the pandemic phase. The manual of the Federal Office for Civil Protection and Disaster Assistance also makes such a recommendation.
In order to ensure that employees can be warned at short notice and do not first appear at work, employers may also request and temporarily store the current private mobile phone number etc. of their employees. However, this can only be done with the employee's consent; there is no obligation for employees to disclose private contact details, but it will regularly be in their own interest.
It is crucial that the collection of private contact information is done for clear, concrete and legitimate purposes. In particular, the purpose is to reduce the risk of infection for employees. At the latest after the end of the pandemic, the collected contact data must be deleted by the employer. It would not be permissible under data protection law for this data to be used "through the back door" at a later date to establish contact after work or at the weekend or for other purposes.
Source: The Baden-Württemberg State Commissioner for Data Protection and Freedom of Information (available at https://www.baden-wuerttemberg.datenschutz.de/faq-corona/)