More SRD info to use:
City Buildings
Cave-Ins And Collapses
Something else to have is a crowd watching. A persuasive PC can direct the crowd to help by forming a bucket brigade, for example.
The Dungeon Master's Guide II details Burning Building as an Archetypal Location on pg. 48.
There has been a couple of firefighting scenarios in the Shackled City adventure path.
Chapter 5: The Demonskar Legacy has a burning inn in Event 18: A Fire In The Night.
Chapter 9: Foundation of Flame has a burning building in Event 37: A City Aflame.
I also remember in the movie Donnie Darko where Donnie burns down the house of a motivational speaker he ridiculed at a school assembly, thereby exposing the speaker's secret "kiddie porn dungeon". What kind of secrets can be revealed by the burning of a building in your game?