It is my understanding that other, non tuition fee expenses would not fall under the Tuition & fees budget category but rather the Institutional Allowance or Trainee-related expenses category. That category is more broad and allows for other expenses which defray the cost of the training. This could include books, travel, health insurance, etc. but you mentioned Metro Pass. I would advise caution on that expense as the policy is specific and states that "funds may not be expended to cover the cost of travel between the fellow's place of residence and the domestic training institution, except that the sponsoring institution may authorize the cost of a one-way travel allowance in a an individual case of extreme hardship" (See policy text
http://grants.nih.gov/grants/policy/nihgps_2011/nihgps_ch11.htm#_Toc271265032 ). I would interpret this to mean that we can not buy a Metro Pass for a trainee to use for getting to/from campus.
Hope that helps.