In very fine print at the bottom the it will list the services it can be used on so they certainly could be reused. I use it as a way of checking that a train that is indicated as being at platform on RTT but isn't yet announced is the right one!
I've sometimes seen the incorrect sticker used on GWR e.g. showing a Bristol bound service as stopping at Didcot on one of the services that doesn't. Would a passenger have any recourse against the TOC as a result of this?