I've seen this in all SAP projects that have outsourced resources in India. No matter their company. EY is just one in a big list of huge consulting firms.
Some just adapt to CET time (when the project is based in Europe). But others start working on India time (GMT+5) and finish working on EST time (GMT-5).
I remember I started using more Skype after it MSN Messenger.
But I'd say it got killed by WhatsApp on mobile phones.