I doubt you'll find a definitive answer. It will normally vary by hospital and policy or common practice. For example, anecdotal evidence seems to indicate that you're more likely to be tested if you are on public insurance (based on some past threads on the topic, etc.). There are probably hospitals that test everyone but I doubt you'll find it advertised. The reality is that you sign a blanket consent when you enter the hospital for care so they aren't obligated to inform you if they do it.
Mama to DS (6/07) , DD (6/09) , and DD (07/12) ..