Did Obama start from square one, zero, a clean slate when he reassembled Bush's disbanded Osama CIA task force?

No. He contacted the AARP and asked them where OBL was. Remember, the big break came 4 years ago when Osama turned 50. Anyone who has reached the age of 50 knows that somewhere and somehow, the AARP will find your address and add you to their mailing list. That is one organization that you can't hide from.