I'm aware of the 319 in Harare, which is of no use for helping with the routes from Dar, is totally under-utilised, and is due to be replaced by an E190.
FJD, the one remaining in Dar is the one they own and which is up for sale, but that can't do all the schedules which is why so many have been cancelled with no notice to the travelling passengers.
It's no good having new leases starting at end of October when the present ones ended at the end of September. I did hear that 1 190 may be en-route, but that's scarcely likely to be in a position to help out for some days and meanwhile FJs already poor reputation takes another hammering. I'd be very reluctant to use them again even if their fares are cheaper - I prefer reliability