The Winging Tally shows Rolls Royce has its engines on 273 787's or times two it has delivered 546 engines to its Boeing customers. Package "B" engine review equals 166 as mentioned above. It was reported that Rolls Royce has 380 affected engines for inspection delivered to 787 customers. In total the affected Rolls Royce engines now tally 546 engines under review or needs fixing. These numbers don't include spares but do address units flying with paying customers. Otherwise, the whole lot of 787 Rolls Royce Trent Engines are now under a review or needs immediate fixing. The FAA has restricted the 787 with Rolls Royce Package "C" from flying 140 minutes away from an airport. The ultimate and prior rating was for 330 minutes from any applicable airport, The 2 hour and 20-minute flying window hobbles Rolls Royce customers to lease older airframes or models as a fill-in while the 787-Rolls remains grounded or under a mechanical fix process.
The company just announced a 10% across the board lay-off of employees while it halts certain field and production operations until a resolution is completed. A speculation is that Rolls was chasing the GE engine performance and it pushed through solutions within its jet engineering that failed to hold up during airline operations. It also may end up making the Dreamliner a one engine aircraft if Rolls doesn't solve its current engine crises. A situation GE would love to address with Rolls Royce customers having Dreamliners.
FYI:
Is it possible to re-engine aircraft with different engine options?
The two different engine models compatible with the 787 use a standard electrical interface to allow an aircraft to be fitted with either Rolls-Royce Trent 1000 or General Electric GEnx engines. This interchangeability aims to save time and cost when changing engine types; while the previous aircraft could exchange engines for those of a different manufacturer, the high cost and time required made it rare.
The benefit of interchangeability makes leasing aircraft easier for the lessor, as their fleet would be compatible with all the airlines and their existing facilities.