OpenSIPS is the sister of Kamailio, both being the result of a fork of OpenSER. Sipwise actually uses Kamailio as the core routing engine, and provides (as Open Source) all the building blocks like provisioning APIs, billing and rating systems, web interface etc. to create a fully fledged telephony system from start to end. Asipto's founders are the core contributors and co-founders of OpenSER/Kamailio, so Asipto provides the core competence in SIP routing and Sipwise offers the know-how of building highly available and scalable SIP systems.
Yes, OpenSIPS is used at telcos to create SIP services. Just be aware that it's more or less the same as Kamailio, which we use as SIP routing engine, and that it's only around 20% of what makes a telephony soft-switch.