July 12 (Bloomberg) — BP Capital LLC Chairman and Chief Executive Officer T. Boone Pickens, who\u2019s been saying for more than a year that Congress was poised to pass his plan to subsidize natural-gas vehicles, may not have been expecting opposition led by fellow billionaire Charles Koch.   Koch Industries Inc., Dow Chemical Co. and the American Conservative Union all have weighed in since May against a Pickens-backed bill that would provide tax breaks to purchase natural-gas fueled trucks. Deirdre…