Typically, when two licensors deliver a release with the same ISRC and the labels have different rights to the asset in different territories, royalties for the given track will depend on the territory in which a user is streaming the track.
For Spotify specifically, if the labels have the same rights in the same territory, the payout is dependent on whichever asset (track URI) a user is streaming from. The streams will be allocated to the provider of the given asset (track URI). For more information on track URIs, click here.