First thing > Pan asked you two questions, and you answered none 🙂
Then, to summary, let’s say there are 3 zones:
Zone A: Nortel 2G/3G BSS – what NSS ??
Zone B: Ericsson 2/3G BSS – what NSS ??
Zone C: Ericsson 2/3G BSS – what NSS ??
If you use any MS (except K660i), reselection occurs from 2G to 3G and from 3G to 2G in Zone A, B and C.
If you use a K660i, the reselection occurs 2G -> 3G & 3G -> 2G in Zone A and B, but only 3G -> 2G in Zone C.
Note: you hint that you didn’t try the reselection in Zone B with the K660i yourself, someone else did. Are you sure they performed the reselection in both directions?