I have an iOS7 app which registers for background mode remote-notification:
-(void)application:(UIApplication *)application didReceiveRemoteNotification:(NSDictionary *)userInfo fetchCompletionHandler:(void (^)(UIBackgroundFetchResult))completionHandler
No, It won't work. Because your app will be in Not Running state as you rebooted your device.
As per apple doc, the new multitasking API(fetch and remote-notification) will work only when the app in the suspended/background/foreground state. If the app is in background/foreground state, then
application:didReceiveRemoteNotification:fetchCompletionHandler will get triggered. If the app is in suspended state, then
-(BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions will get triggered.
In your case the app is in Not Running state, because of that
application:didReceiveRemoteNotification:fetchCompletionHandler is never get triggered.
Please refer apple doc for more about app states.