At 12 pm August 15 1998, The Family Channel turned into Fox Family. I remember seeing a countdown (from 10 I believe) and then orchestral music played while images/short clips of the new program were shown. A short lived European cartoon called "The Three Friends and Jerry" aired immediately after, so a recording of this episode on this date would likely produce what I've been searching for.
I've found a schedule for the launch day though (below). Not too hopeful on this but any help is appreciated!