I recently had this type of job, it was residential job just a standard 3 bed semi, 1 egg was on window above conservatory. I soaked with wfp left 10mins and then wfp scrubbed but no joy. I used a procurve pole with a mop on and scrubbed with that, still not taking it off! I then used some neat ungers gell on the mop and then used a 6inch blade on the pole. Then wfp, this did the trick. I was worried about scratching the glass but the ungers gel was an excellent lubericant for the blade. If egg was accessable by ladder then would be quicker to remove by hand but I found the experience to be beneficial as now I know it can be done without a ladder if necessary.