Hi @Anonymous User
I couldn't find anything in the Sky Sports Box Office FAQ's, but under the NowTV box specification it mentions a minimum download speed of 2.5 Mbps which would suggest to me the stream would be 720p 25fps (similar to the NowTV sports live streams) so i doubt very much you will get 4K from the Sky Box Office App on your NowTV 4K box.
https://sports.skyboxoffice.com/faqs/ssbo-faqs
You could ask Sky Box Office live chat and get an official answer from them.
To reach their live chat service, open the link above and a small black pop up box should appear on your screen saying "Chat with an Expert" click the black box and a web based chat service should appear on your screen .
