Here are three images of some NTSC video captured on an Agilent DSO6000 series
scope.

The images show the use of what on analog scopes would have been the sort of
thing you could see with delayed sweep, except that here it's pre-trigger sweep.
This was captured in single sweep mode; it wasn't triggered as a repetitive
signal.

The full vertical interval of the video signal (16.6 mS of signal) is captured
and displayed in the top half of the screen. A movable small width window is
shown as a pair of vertical lines in that top half. The signal in that window
is shown expanded in the bottom half.

The first image shows the video 15 mS before the trigger event, with the
expanded portion shown at 20 uS/div. You can see line 21's closed caption data,
followed by the first line of active video.

The second image shows the same thing but with the bottom half at 500 nS/div,
showing the color burst.

The third image shows the color burst at 50 nS/div. This scope could continue
to 2 nS/div.

All this is zooming in on signal 15 milliseconds before the trigger. The zoom
window can be positioned anywhere in the 16.6 milliseconds worth of video and
examine the signal with 2 nS/div sweep speed.

Have there been any analog storage scopes that can do this with a single-shot
capture?

And, if you were to spend the $28k that the Iwatso TS81000 costs, you can get
much better performance than this.