Boris

It is possible.

Asterisk

Install Axon PBX, configure it to operate with Vonage, configure Linksys to login at Axon's internal number, configure softphone same way as linksys to second internal number. In this case you will be able to make and receive calls with linksys and with softphone. Also will have possibility transfer call to IVM if linksys or softphone do not answer.

After half hour of exploring IVM, I have created menu for call transfer. First it requests pa password then a number to dial. Also possible to skip password according CallerID. Just look OGM properties and your will see all necessary settings.