toronto reuters canadian buyout firm onex corp is leading the bidding for swiss juicebox maker sig combibloc group, bloomberg reported on sunday, citing unnamed people familiar with the matter.officials at torontobased onex, canada&39s largest listed private equity firm, did not immediately respond to calls seeking comment.the report said onex may reach an agreement to buy sig for more than 4 billion as early as this week, but that negotiations could still fall apart.reuters reported in june that new zealand&39s richest man, graeme hart, was exploring a sale of sig, the world&39