I haven't seen these stripes (not a football fan!), but there are
currently afoot legal/financial wars concerning using such "special
effects" for "on the air real-time added advertising" like, eg.
1) electronically replacing a real advertising sign with a computer image
"sold" to another company - which would "play" whenever a camera looked at
the real (now undesired) sign on the field fence.
2) electronically inserting into the network broadcast of a movie a
consumer product for purposes of sellable "added advertising" - eg. adding
a coca-cola bottle on a table top, as if it were in the original movie.
It is my impression/intuition that all of this is purely electronic and in
real time.