Is Silent Remote Notifications possible if user has disabled push for the app?

This matrix might help. At left hand side, it shows if "didReceiveRemoteNotification: " method will get called or not. Other two columns is related to setting app. Settings -> YourApp. If yourApp supports Notifications and background app refresh. Look into matrix to check when you app will receive silent push.

Short answer, yes

The exciting new opportunity for app developers in iOS 8 is that Apple will now deliver “silent” pushes even if the user has opted out of notifications. Also, “silent push” is no longer just for Newsstand apps. Every app can take advantage of this ability to refresh content in the background, creating the most up-to-date, responsive experience possible, the moment the user opens the app.

Although...

Users still have the ability to switch off your app’s ability to process a “silent push” by means of the “Background App Refresh” control. Even though Apple Push Notification service (APNs) will deliver a push marked “content-available” to your phone, the OS will not wake up your app to receive it, effectively dropping it on the floor. However, opting out of “Background App Refresh” is a lesser-known capability not directly associated with Notifications. You don’t access this preference in your Notifications Settings--it’s located under General > Background App Refresh screen.

Keep this in mind when building your application.

Source: https://www.urbanairship.com/blog/watch-list-ios-8-opt-in-changes