If it matters in a velodrome where the given distance is probably less than 2 miles, then over a race of more than 30 miles, or crits that last more than 30 minutes, it would be highly probable that there is always a point where the weight aspect of a bike matters. Of course, the beauty in the sport is that it's more complex than that. This can be described through acknowledging the different factors at play. And, all things summed up as net forces, we could likely find various situations where the difference between a 15lb and 19lb bike are negligible or not as dominant as other factors.
I would assume that this is simply redundant review by now for most. Aerodynamics, rider skill and weight, racing conditions, bicycle characteristics, etc, etc..
Equipment certainly matters. But by equipment, at least in my definition, that also involves the engine.
I've seen 1996 Supras dust off some Lamborghini Gallardos at a rolling 60. The brand of car only told a very very minute part of the story. Same application here.