You can buy Indian numbers with Twilio and make/receive voice calls and text messages. (See their site.) After the call hits the Twilio infrastructure, it is as location-agnostic as any other application interacting with APIs on the Internet. (One thing I do with Twilio is forward calls made to a US number to a Japanese number after doing trivial processing on them. My app runs on a server which happens to be somewhere in the vicinity of Chicago, not Japan.)

I'd assume things are roughly similar for Plivo/Tropo but I don't use them.