As far as I can tell it accepts RAWs but uses the embedded JPEG on iOS.
Using RAW images with iPhoto for iOS - Apple Support Which would be a bit pointless—you might as well just save as JPEG.
I'm not sure how this works with photos which are imported into OS X Photos as RAW, have modifications made (which would affect the converted RAW file) and are then synced and viewed/edited on iOS. You'd then have modifications applied to two different source images, the converted RAW and the embedded JPEG. That doesn't sound proper.
I've looked into this a bit more, with a view to using an iPad to review photos on the go when I'm out and about with my Fuji rather than dragging a laptop around with me just so I can look at pictures on a decent sized screen (might as well stick with the Nikon outfit if I want to do that, bring a 3kg tripod along too.)
As far as I can tell this is the situation, although I've only been fiddling with this for a day or so and my previous exposure to iOS has just been using the phones mostly as phones plus a brief play with the wife's iPad, so I might have misunderstood something:
You can import jpg and (recognised) raw types onto an iOS device, for example by using the SD-Lightning adaptor or some sort of wireless connection (which I quickly decided to avoid because Fuji native wireless appears to be a shit implementation). Either way they end up in the opaque Photos database rather than on a file system.
You can look at jpgs or the embedded jpgs in the RAW files on there, and probably fiddle with jpgs using Snapseed or whatever if you're so inclined, but to do anything with raw files on an iOS device you have to use either Adobe products (in which case you're involved with
two totalitarian cloud regimes), or obscure third party apps, each of which is a bit flaky in different ways.
You can sync Photos with other Apple devices, e.g. a Mac where proper raw editing tools might exist, via iCloud or iTunes. This seems to work until you actually try to export the files and edit them, in which case issues may arise. I just experimentally went this route with some Fuji .raf files but can only read them in Rawtherapee and Silkypix, Capture One won't have anything to do with them if they've been tampered with by Apple Photos, even if you use the 'Export Unchanged without fucking about with my files in any way, even if you think it's for my own good" option and didn't edit them in any way in Photos.
Or you can try to avoid iCloud/iTunes and use some sort of third-party sync, e.g. via PhotoSync or Shuttersnitch apps and Dropbox or something else, in which case iOS will try to mess you up at every stage and OSX isn't much better. For example, only iCloud seems to be able to do anything in the background on iOS, so anything else you try to use is going to clog your device up for what can easily be hours. Anything involving wireless will also be fucked by the iOS device dropping the connection every few minutes.
It's the latter especially that has me thinking that Apple are perfectly happy to create a wretched user experience for anyone on iOS who isn't willing to pay for iCloud and settle for whatever RAW editing capabilities they may choose to give you in their proprietary software. This is far worse than the minor annoyances of OSX, which can usually be avoided by invoking the perfectly good BSD stuff underneath the pretty GUI when you need to be completely in control of what's happening to your files.
I can see an "iPad on the go" solution being ok for jpgs (which are so good from the Fuji that actually might be workable most of the time) if you don't mind being locked into iCloud and Photos, but I can't imagine how they're going to sell the new giganto-iPad to photographers who habitually use RAW without sorting this horrible situation out ...