Can Swisscom guarantee legal compliance for a contract signed with its electronic signature?

Swisscom can only confirm issuing qualified electronic signatures in legal jurisdictions of the EU according to EU regulation eIDAS and Switzerland according to Federal Signature Act ZertES.

According to ZertES, Qualified signatures are only accepted in Switzerland, and qualified electronic signatures, according to eIDAS, are recognized in the EU/EEA. 

Only a lawyer can verify if a qualified signature complies with any contract. It's related to the signature and other aspects that may be agreed upon in the contracts, e.g., legal status, legal domicile, the requirement of return by registered mail, etc. In these cases, it could imply that no electronic signature is accepted and that a paper-based process is still mandatory.