Well, easyJet for example uses Flightradar24 as main source on its flight tracker.
If you fly a late evening flight you can see from the morning where your plane is and you can also see if there is an aircraft swap with another base.
Last week I was in Paris, I had a late evening flight to MXP, even though Flightradar24 on my flight was monitoring a plane doing a rotation from LPL base. They swapped the plane on ground in CDG. I guess for easyJet, FR24 have access to the plane assigned for each rotation.
PS most of the time on late evening you can see which flight is the plane doing the following morning too