You are right that there are no mandatory requirements for employer-provided transportation. Your company does not need to provide this benefit to its staff.
However, you might be making an incorrect assumption by thinking that there would be added liability if you provide such transportation. In fact, injuries that occur to employees on their way to/from work are regarded as work-related injuries under China law, irrespective of who provides the transportation. In other words, your company is already liable for these sorts of injuries so long as they occur to/from work. Providing transportation does not change this liability or add to it.
According to the Work-Related Injuries Regulations, a work-related injury occurs if an employee is injured, handicapped, or killed in a traffic accident, due to a reason that is not attributable or mainly attributable to him, on his way to/from work during such hours that correspond to the business start and end times and by such route that he must reasonably take. Locally, the recently-issued Beijing Work-Related Injuries Regulations also provide for the same definitions. The definition is thus fairly narrow. For example, let's assume that an employee is going home after work and stops at a market on the way to purchase some yuanxiao. After leaving the market, he is hit by a car. Generally this would not satisfy the "such route that he must reasonably take" requirement of the regulation because he did not go directly home after work.