The preliminary issue in the question is fast food restaurant is vicariously liable for the Cathy’s negligence. Since the concerns about the law of tort, the following analysis will focus on the possible tortuous liability instead of the potential breach of the contractual obligation and the criminal acts.
In principle of vicarious liability, to make an employer liable for a wrong committed by an employee, the plaintiff must establish that: 1. defendant is an employee ( as opposed to an independent contractor); and 2. The defendant committed the wrong in the course of his or her employment.
First, the court will apply different tests to determine the existence of an employer-employee relationship. These include the control test, the organization and integration test, the economic reality test and the mutuality of obligations test. In this case, we could use the ‘control test’ and the modern approaching test ‘the economic reality test’ to examine the whole issue. Similar to case Chan Ming v. Wayfine Investment Ltd 2 HKLRD E12, Cathy received an order of delivery, she had indicated what goods were to be loaded in the restaurant and where to be left in the delivery destination(the food buyer). So, Cathy would be an employee.
In Lee Ting Sang v. Cheung Chi Keung and AnotherHKCA 315 and Chan Kwok Kin v. Mok Kwan Hing & another , the court applied the ‘the economic reality test’ to examine the existence of an employer-emplyee relationship. Likewise, Cathy drives the motorcycle which provided by the fast food restaurant; She doesn’t hire any her own helper; She doesn’t take any financial task on her person takes; She has no responsibility for the investment and the investment. Therefore, the fast food restaurant would be her employer.
Second, the court has to prove that the wrongful act of Cathy was done in the employee’s course of employment. A wrongful act is done within the course of an employee’s employment if it is either 1. a wrongful act authorized by the employer; 2. or a wrongful and unauthorized mode of doing some act authorized by the employer.
It means if the accident occurs because Cathy was racing with other vehicles, in defiance of an express prohibition by the employer against racing. Or she is not driving to the motorcycle without permission. The fast food restaurant is not vicariously liable for the negligence. Since Cathy does not commit the negligent driving in the course of employment. What she has done is unconnected with her employment and the fast food restaurant cannot be made liable for them. It would be determined by the test called the ‘close connection test’, which is laid down in ‘ Ming An Insurance co(HK) ltd v. Ritz Carlton Ltd.
There is a hidden issue in this case. It said Cathy drives a motorcycle which was assigned by the fast food restaurant. It would be a vicarious liability of the car’s owner issue arise. sIn Kung Kit Shing v. Star Synthetic Flower Factory (A firm) and Others  HKCFI 73; HCA8967/1981, the court considered that the registered owner of the vehicle can be held liable vicariously for the wrongful act of the driver. It means if the motorcycle which is assigned by the fast food restaurant is owned/ registered by another contractor or party, the owner is also vicariously liable for the wrongful act of Cathy.
In conclusion, basis on the above analysis, the fast food restaurant is potentially vicariously liable for the negligence of Cathy. The pedestrian can seek for the remedy from the fast food restaurant.