I could see this happening more often because in many fare rules, EWR/JFK/LGA are co-terminals. In the past, when I've volunteered for an oversold flight going to LGA, the agents have also offered to route me to JFK.

I remember during a storm situation in the past, I was stranded in TX and was trying to make it back to BOS. My original flight was for Sunday, but the earliest they could get me out was Tuesday. Unfortunately, I had another AA flight leaving out of BOS on Tuesday, and their alternate booking wouldn't have gotten me back in time. I asked if they could just route me to ORD on Tuesday, but the EXP AAgent said that the ticketing rules for the storm accommodations only allowed her to route me to airports within x00 mile radius of my final destination. (I think it was 200 or 300 miles - not sure.)

I wonder if AAgents also have that x00 mile radius leeway during VDB situations...