The Queue System has a failover recovery feature - if the farm contains multiple servers running the Project Web App Application ...

The Queue System has a failover recovery feature - if the farm contains multiple servers running the Project Web App Application Service, and the Queue Service fails on one server, jobs are automatically redistributed to other servers on which the Queue Service is online. A Queue Service is considered to have timed out if it cannot be accessed from the Queue health timer job for more than the 'Queue Timeout' interval.