Nope. The Terms and Conditions of the offer explain why:

This offer is valid for up to six passengers traveling together. The first two passengers are at regular (full) adult rail fare, or may use the AAA adult, Student Advantage, Veterans Advantage, and NARP discounted rail fares. The third through sixth passengers will receive a 90 percent off discount from the regular (full) adult rail fare. Seating is limited and subject to availability. This offer is non-refundable. Reservations must be made at least three days prior to departure. The companion(s) and paid adults must travel together at all times and have tickets issued at the same time.