Oil / gas pipeline above ground doubling as a monorail train
You have really asked two questions. Is it technically possible? Is it feasible?
While the details of this subject are not my area of expertise I can make a couple of general comments. First given the proper motivation, time, and funding many things are possible. After all we put several men on the moon. However for both trains and oil/gas lines to be feasible the goal should be not only what is possible but also what is economical, safe (human and environmentally), and what is acceptable to social-ital perceptions. The additional factors are where I would have to question the feasibility of your concept. I also have to admit I'm not sure where to get a more definitive answer without the time, expense, and location specifics of a project analysis.
Thanks very much for your insight, Karl V.