The people responding are volunteers too. Operators are not standing by to answer the call.
The answer is it's all a matter of how hard they look. However, I'd be surprised if they didn't. Private background checks will find ten year old misdemeanors, let alone felonies. The trick is that you need to know what state's records to search. Obviously if you are in California and your conviction was in California, it will be obvious. We also run checks on the state the person is relocating from, has been previously employed in (from their resume), and went to school in. Of course, that wouldn't catch some Pennsylvania kid who got charged down in Ft. Lauderdale on spring break, but a 50 state check is quite a bit more expensive than checking one or two.

