Thank you mvut,
But, "In order to enable PWM output then set ATP0 and/or ATP1 equal to 2 (this will only convert for A/D-0 and A/D-1 respectively).".
I tried to output two separate ADC channels but as I understand the XBee is only able to output either A/D-0 or A/D-1 on both PWM0 and PWM1.
On the other hand, I've managed to send all readings with UART.