Q: If I have employees out of work either due to FMLA, or maybe even if they are on furlough due to a business downturn, can I still require that they be on call or respond to emails?
A: This depends on the individual circumstance of the employee. If an employee is out on FMLA, depending on the reason, you could discuss with that person, preferably before FMLA is taken, about if they would be available to respond to questions, whether by call or email. You should not force a person who is taking FMLA to respond or be on call. Further, any time spent responding to questions, answering emails, or otherwise doing work, would be considered work time and would not be counted against an FMLA allotment. It would also be paid.
If an employee is on furlough due to a business downturn and is not being paid but may be required to assist with various projects on an intermittent basis, you would need to discuss with that employee how that process would work and that all time spent doing work would be paid. How this occurs may be different for exempt and non-exempt employees.