Dialstatus question

When making sip or iax2 calls yesterday I noticed that all calls from the manager interface to a busy number exited with dial status = busy.
However today, the same busy number, the same voip providers, I see dial status = cancel.
I tried all 3 of my voip providers and got the same response.

Is there some variability in what the local teleco will give in response to a busy phone number? Clearly asterisk can detect busy dial status.

Asterisk 1.2.24, freepbx 2.2