Matilda Scorpion flail tanks were used at 2nd Alamein but they were unreliable and most mine-clearance had to be done by hand, did this have any impact on the British plan?
the plan at el Alamein? I doubt it had any effect. Scorpians were only beingt tested and in small numbers and the mine fields were massive and deep. Plus the Allies only needed and planed to clear narrow tracks through them to allow a push out. I am surprised the allies allowed such new technology to be used especially given that these were in the plan for d day FNG
it removes the element of surprise and allows the enemy an opportunity to watch them in action and prepare counter measures. D day was far more important that el alamein strategicly and thus the better place to use them for the first time. FNG
It appears Grant Scopians were used in Sicily. http://en.wikipedia.org/wiki/Mine_flail And it looks like the Soviets were using various minclearance devices already - look at the wiki links to mine-ploughs and rollers
Personally I don't know but for the most part I think these mine-clearing vehicles are still in their early phases of being developed and fine tuned.
Having more armored mine clearing vehicles available would have helped. The engineers were exposed to artillery and small arms that greatly slowed down the clearance of lanes and limited the number cleared. This led to bottlenecks that were more easily covered and limited the British ability to bring their full strength to bear.