Company A maintains a 401(k) plan for its employees. There is a classification of employees which A requires to undergo a 3-4 week training period. If the prospective employee successfully completes the training period, s/he is appointed an employee of that classification. Company A counts eligibibility and vesting service from the date on which an individual is appointed to the status of an employee of the classification and not from the commencement of the training period. Is A permitted to exclude the training period from the calculation of eligibility and vesting service? Does it make a difference if the plan document states that service is counted from the date that an individual is appointed to a certain status?

Can't be done. All service is aggregated with very few exceptions (none of which apply here). I'm assuming these were paid employees?