How does boiling water revive cut flowers?
I could not find any scientific papers that have done research into this phenomenon but the general reason given for wilted flowers to being resuscitated is given as the hot water being absorbed faster and I quote


  Florists use warm water only for resuscitating wilted flowers, because
  warm water is absorbed quickly. For restoring wilted stems, hot water
  (110 degrees Fahrenheit) is recommended. For woody or badly wilted
  stems, very hot water (180 to 200 degrees) is better. Florists then
  move them into a refrigerator (reference).


The reason for absorbtion faster is given as 

luke warm water in a vase arrangement because warm water is “thinner” (has fewer air
bubbles) and moves up the stem faster than cold water (reference) and Warm water molecules move faster than cold water molecules and so can be absorbed by flowers with greater ease (reference).