Unassigned Work Orders

Create a workgroup called 'Jobs not Assigned' (Go to Settings->Manage Lists->Job Groups)
Create a dummy user called 'Jobs not Assigned.' Then assign it to workgroup 'Jobs not Assigned' (Go to Settings->Manage Users->)

Job Groups

Go to each Service Provider's profile and make them 'Team Lead' of this workgroup, 'Jobs not Assigned.'

Jobs not Assigned

Assign these unassigned work orders to this dummy user 'Jobs not Assigned.' Your service providers can now see these work orders on the mobile app.

Note: Have the Service Providers log in and back into the mobile app for the changes to take effect.