I didn't use DISA very much with the STSe, but I will take a stab at it. When you say "reorder tone is returned" is it after dialing the entire co line (88+xxx) or is it before you can finish the sequence? The manual show's that you only have 2 options...Either dial 9 or 801-823. It doesn't look like 88+xxx is an option. The initail dial tone you receive isn't technically the same you would receive as a digital or analog extension, which means you have no way of programming the COS of the initial dial tone, therefore no way to access on a per line basis. I may be wrong, but it looks like it's either 9, or group 801-823 are the only choices you have. Maybe someone else can clarify.

"I thought I was wrong once, but I was mistaken"