I have to scrub a bunch of phone numbers for disconnected numbers. How
do I do this programatically without dialing the number? (I'm not
worried about making a connection to the PSTN to find the current
phone status, I just don't want to ring up all those people just to
check their phone status.)

I had a similar problem.  I asked the phone company to do it for me. 
I was getting a business line and they ran the list for me.