Will batt insulation ignite if it is laying against my steam pipes?
Maximum temperature of a household steam system is all of 250F, so not even paper will ignite from contact with steam pipes in a house (15PSI) boiler system. High pressure steam is not found in houses (in modern times - early systems were very dangerous) unless they are in major violation of a lot of codes and safety standards that would be of far more concern than the insulation used.

"Batt" insulation is typically either fiberglass or mineral wool and thus not flammable anyway. Even cellulose (paper fibers) insulation is treated to reduce the threat of fire, and again, 250F will not ignite it anyway.