You can light TNT in spawn protection, through the use of a flame bow

Start a server and join it

Give yourself operator permissions

Set the world spawn to your current location

Place a block of TNT or TNT minecart within spawn protection

Obtain a bow enchanted with flame

Give operator permissions to a different player

Remove your operator permissions

Shoot the bow at either TNT or a TNT minecart within spawn protection
-Notice how they are lighted and destroy blocks within spawn protection