Можно ли использовать существующую АТС с Exchange 2007?

Это один из популярных вопросов на Платформе 2007. Собственно, а как подлючить АТС к Unified communications в Exchange 2007?
Есть такие странички Поддержка IP/PBX и АТС и Поддерживаемые шлюзы IP/VoIP, где по-русски все написано.

А также был найден пост у Eileen Brown:

Now this is useful - I get loads and loads of questions about this subject.  If you have a Dialogic gateway and are thinking of Exchange 2007.  Dialogic has rolled out it's new website at  .  This website focuses on Dialogic Gateways that are certified for integration with Exchange 2007 Unified Messaging.  These gateways support popular integration options to telephone switches too.

• Eight to 120 ports of Voice over IP and Fax over IP connectivity per gateway
• Tight integration to leading legacy PBX's from Nortel, Siemens, Avaya, Alcatel, Mitel, Ericsson, Siemens, and NEC
• Easy installation and maintenance with web-based configuration and remote management capabilities
• Investment protection for legacy equipment that also enables worker productivity enhancement solutions such as Unified Messaging.
• Support for SIP and SIP supplementary services such as message waiting indicators, transfer, hold, park, and caller ID functionality