оно?
var str = '<div class="engage-eventCallout">{^youtubevideo|(width)425|(height)264|(rel)True|(color1)#666666|(url)http://www.youtube.com/watch?v=ZqUFLFmuLmg|(autoplay)False|(border)False|(loop)False|(cookies)False|(hd)False|(fs)True|(color2)#EFEFEF^}December 16, 2011 Seattle WA</p></div>';
alert(str.match(/\^youtube.*\^}/)[0])