QuoteEach line is connected to one set of cordless phone A(Line1) and B(Line2)
You use the word "Line" ambiguously. Let me use SP and Phone instead. It's important to understand that each phone can be set up to make and get calls over each provider.
You can't control what happens "when SP2 is busy" via DigitMap. But why would you want it? Do you get only one channel per provider?
If Phone 2 is busy, you pick up Phone 1, right? You
can set up different rules for Phone 1 and Phone 2. Maybe, it will help if you describe rules separately for each phone. For example, "from phone 1 international calls (011xxxxxxxxxx) will go to SP1, and local calling (911,1905*,416*,647*) will go to SP2". "From phone 2 (911,1xxxxxxxxxx) go to SP2, and international calls (011xxxxxxxxxx) will go to SP1"
Then you will see that the rules are exactly the same for Phone 1 and Phone 2
Last, these rules assume that you will dial all digits. Alternatively, you can make OBi add or remove digits. For example, if you dial 819876543210, Obi will know that you call Japan and add 011.