I keep running into this and I'm wondering if there's a reason behind it I'm missing:
On new installs, many installers opt to make the second line on a phone in another range (e.g. 2215 and 3215) using SCR keys instead of two lines with the same number using MCR keys (e.g. 2215 and 2215).
I love MCR keys because it doesn't confuse the users wondering what this other extension is. I have consistantly re-programmed phones to have multiple MCR keys.
Is there any reason NOT to do what I'm doing? It seems to make sense, but on almost every install I have encountered, 2 differently numbered lines are what have been programmed. Why do that as a default?