Back in the '70s, I personally saw tracers start grass/brush fires at two consecutive military firepower demonstrations (a year apart in time). More recently, our county-run indoor range experienced a near-catastrophe because some knucklehead ignored the range rules and shot a few tracers before he was stopped. The backstop is primarily constructed of shredded tire rubber which is nearly impossible to extinguish when burning. A miracle that we didn't lose the range.
About a month ago, sparks from steel-core ammo on steel targets started a brush/grass fire which burned 18 acres before the forest service and local FDs could bring in enough heavy equipment to contain and extinguish it. There was a brisk wind that day; had it blown north instead of south we would have lost half the range infrastructure at least.
I shoot a night match once a month. Some of the berms have tires on them to help stabilize them. It's normal to see sparks from regular FMJ AR rounds hitting the steel tire treads and not unusual to smell burning rubber, although I've never seen anything actually produce flames.
So, I agree with jimmykm21 - it depends on conditions.