There are also mobile features that work without the desktop dock. For example, UCCaaS can transfer calls between a desk phone and a cell phone in the middle of a call, said Roberta Mackintosh, director for global unified communication and collaboration. For example, a user could stay on a conference call when leaving the office. The platform can carry this out regardless of who the employee's mobile operator is, Mackintosh said.

In time, Cisco's Cius tablet also will play a role in UCCaaS, according to Verizon. and is scheduled to ship in March with Verizon Wireless as its first carrier partner.

One thing Verizon learned from its trials of UCCaaS was how much enterprises want to customize their UC deployments, Mackintosh said. For example, they want to integrate the UC software with the applications they use in-house and control upgrades to the software used in the platform. UCCaaS will give them that kind of control, she said.

Getting UC as a service can help enterprises both to save money and to fine-tune their UC implementations, according to analyst Cindy Whelan of Current Analysis.

"Verizon can make applications available to the enterprise that they only need for a subset of their employees," Whelan said.