I guess you're on your own, or have to rely on police/security. I'm less concerned about being allowed to carry in a courthouse as I am my wife being able to carry to the mall or Walmart where people love to prey on women who are alone. I believe these are the places generally forbidden in Texas:
School buildings
School grounds where a school sponsored activity is on-going
School bus, or other school passenger transportation vehicle.
Polling place on election day (including early voting)
Court or court office.
Race track (licensed for betting)
Airport secured area (past metal-detectors in terminal building)
Within 1,000 feet of a place of execution on the day of an execution, but only if given notice
51% locations - businesses that derive 51 percent or more of its income from the sale or service of alcoholic beverages for on-premises consumption.
High school, collegiate, interscholastic, or professional sporting events.
Correctional facility
Amusement parks
Businesses can also forbid carry by posting a
30.06 sign (interesting choice of numbers), but I don't see that it's forbidden to carry on a public transportation here. I could be wrong...