I am not LEO. It has happened at my home a couple of times. Once, dispatch called and stated there had been a 911 hangup at my address, but then stated the address of a residence nearly 10 miles away. The phone lines used to be pretty screwy around here, I assume that was the cause.
The other, more recent occurrence was odd. My wife had been on the phone with a relative back east for an hour or so. She hung up and noticed the message light was blinking. It was a message from dispatch about a minute prior to her hanging up regarding a 911 call. I tried calling the "non-emergency" number about 5 times with no answer and that's about the time a couple of SO units arrived.
I explained that my wife had been on the phone at the time and could not have made a 911 call. One of the officers asked if it was a cordless phone (yes) and if the battery was low (yes- that's why she got off the phone). He then told me it happens all the time with cordless phones when the battery is dying. Apparently, the "beep-beep-beep" low battery signal the phone plays in the earpiece can be interpreted as 9-1-1 digits by the telco system.
I had never heard of that, but it seems to be the only reasonable explanation.
Whatever the question, Cilantro is the answer.