Maybe Buildcraft gates will work. I haven't had a chance to try out IE so far, so this is pure speculation, but you can try attaching some kind of Buildcraft pipe to your ovens (any will do, even structure pipes or whatever, they're not supposed to do anything besides holding a gate) and place a gate on them set to output a redstone signal on condition "Machine Has Work". I repeat, I don't know if gate conditions work with anything except Buildcraft's own machines, but I guess it's worth a try.
A more complicated solution (in case the gates don't respond to IE machines) would involve buffer chests or some other kind of storage connected with BC pipes that hold a gate set to emit a redstone signal on "Item Passing Through" or whatever it's called, and put all that stuff in between your AE network and the ovens, so that any components involved in the autocrafting process would have to pass through this buffer setup.
I. e.: AE network -> ME Interface holding the crafting pattern -> Buffer inventory (chest or w/e) -> wooden pipe with autarchic gate set to auto-extract anything and emitting signal on "Item Passing" -> oven/furnace -> back into AE network. Slightly overkill just to get a redstone signal out of the whole process, but it should work (in theory).
