The gate lead/pushback driver's failure to recognize that the provisioning truck was within the safety zone of the gate during his walkaround due to distractions, which resulted in the subsequent collision between the airplane and the truck. Contributing to the collision was the provisioning truck driver's failure to recognize he was parked in the safety zone of an active gate adjacent to his assigned gate, and the guide agent's improper assumption that the safety zone was properly cleared by the gate lead/pushback driver.