I hatch quail all the time. You can incubate them with chicken eggs but don't raise humidity above 40-45% for hatch in still air (50-55% in forced air). They need very low humidity for hatch.
I've had great hatch rates with my quail and chicken eggs. Just have low hatch rates with my turkey and peafowl. Always seem to have a lot that look fully developed and look good at lockdown then never pip.
I use a gqf cabinet incubator and hatcher. Have ran the humidity by hatching charts.
What is the down side to too low humidity during incubation???