Can you do Anulom Vilom/Kapalbhati in office/Seats/Planes/Buses?  

Yes for sure!

Anulom Vilom/Kapalbhati/bhastrika can be done anywhere you can sit.

To Do it in Anulom Vilom office/Seats/Planes/Buses:
Sit on your Work/Plane/Buses/Train Chair/seat. Put your elbow on chair/seat arm. It will give your arm/elbow support. Then put your hand around your nose and you can quietly start doing it. if you do it by just like putting hand on nose like covering nose. People will hardly notice you are doing Anulom Vilom.

Even If people come to know about your secret Yoga then what just explain them you are doing Pranayam.

To Do it in Kapalbhati office/Seats/Planes/Buses:
 If you dont want people to know you are doing kapalbhati wear loose/big shirts. so when your stomach go in people dont notice. Sit on your work Chair. You can quietly start doing it.  

If people come to know you are doing something funny just tell them that you are doing Pranayam who knows people get inspired from you and starting doing Swami Ramdev Yoga:)