The Datasheet states: Supports IGMP managed multicast IP transmission, optimizing IPTV streaming so don't see why they shouldn't work
Although when you look at the individual PLA TL-PA4020P, which is one within the kit, it doesn't mention Multicast??
Broadband Extender 600 Kit or Broadband Extender 600 Flex are what BT supply now, if you've recently ordered BTTV you should be able to request the 600 kit for £20 but if you need the 600 Flex then ask or you may have to buy yourself.
Are you able to connect the Hub direct to your BT TV box and check what you get? This would help elliminate or confirm that your powerline is at fault
Also, does your powerline have two ethernet port connections, and you have PS4 and BT TV plugged into each?