Only soso
You have to manually paste (!) the sticker (figuring that out took me a while), which some apps will allow and some wont. So its a bit of trial and error and can be frustrating. Getting back to the normal keyboard can be confusing too. Going to delete that app, not user friendly enough. Hopefully it will improve in future versions.
Ralfsreview about
Emoji Keyboard by LINE, v1.0