This bill was assigned to a congressional committee on March 15, 2013, which will consider it before possibly sending it on to the House or Senate for consideration. The bill is to amend the IRC of 1986 to provide that reimbursements for costs of using passenger autos for charitable and other organizations are excluded from gross income. As of now the bill has not gotten out of committee.
At this point it looks like it will not be passed or signed into law this year.