Hi,
It most definitely depends on the partition! In order for an incoming call to be routed to a given number, that number has to be reachable from the gateway. This is achieved by having an incoming calling-search-space on the gateway end-point. The CSS simply dictates whom the gateway can call, and therefore the destination number or pattern will be associated with a partition, and it is this partition which has to included in the CSS applied to the gateway.
For example, lets say your incoming PSTN called number is 2000. This number is the DN associated with a Line Appearance on a phone and will be assigned to a particular partition lets say called Internal. Therefore a CSS should be configured which has Internal as a selected partition, and this would be the CSS you apply to the gateway.
Regards
Allan.
Hope this helps, pls rate helpful posts.