SBB (since 1999 SBB Cargo) Sgns cars were not normally used in international (through traffic) unit trains. They were mostly used to transport containers from Container terminals to destination stations in regular SBB freight traffic.
That said, the cars were available to customers who hired SBB Cargo to handle their traffic, which could include operations to and from Switzerland and other countries.
So, for example, a load would arrive at a Swiss Container Terminal from a foreign port. From there, it would be transferred to a SBB Cargo car and would then be attached to a mixed freight train for delivery to it's destination.
Due to the complex relation between SBB, SBB Cargo, Hupac, Swiss Terminal, Contargo, etc, changing partners and shareholders have made the operations of SBB Cargo container traffic rather difficult to follow.
I know that SBB Cargo Sgns were used at one point for transporting container loads between Crossrail's German and Italian terminals and their Swiss base of operations at Wiler. They were also used to transport special containers by Austrian company Innofreight (Woodtainers).
Many companies that would normally be the type of customer for this kind of service from SBB Cargo have instead decided to lease their own cars from other companies, so Swiss Post leased cars from AAE. I could not find information about other operators (RailCare, etc) relating to cars, as most of the information focused on locomotives. Companies can hire SBB Cargo or if they require their own rolling stock, can lease from VTG/AAE, Cemat, Wascosa, Touax, Ermewa, etc.
I would assume that most of the fleet is currently used in what SBB Cargo calls it's Rail & Transfer Services and what it markets as "Swiss Split" Services for Import/Export Traffic.
As I stated before, the complicated links between SBB Cargo and other companies, (e.g. Hupac), where SBB is a stakeholder in Hupac while Hupac is also an investor in SBB Cargo International (etc) makes it hard for an observer to understand how this web works.
If SBB Cargo is competing with one of it's associates, affiliates, subsidiaries, etc for a contract, do they freely compete against themselves?
For example, a contract for traffic between a Swiss Terminal and a German Terminal is offered. Does SBB Cargo bid or is it automatically ceded to SBB Cargo International? If Hupac or Contargo is bidding, does that preclude a SBB Cargo bid?
Coop has it's own rail logistics (RailCare). I don't know whether Migros is a SBB Cargo client for their container traffic.
Ich entschuldige mich fuer dieses Bericht auf Englisch, aber Ich koennte nicht die Woerter und das Sinn auf Deutsch richtig schreiben.