A possible way to implement that would be if the option to craft Tin Buckets was enabled in the IC2.cfg file, GT would disable the Alloy Furnace and Macerator uses of Buckets.
The macerator recipe is added by GregTech.
The alloy furnace recipe can't be removed without Eloraam's permission or a lot of guessing. (Edit: Or a new forum that the IC2 devs can't lock threads on)
Many servers in 1.2.5 and earlier disabled tin buckets anyway because of that.