Is setting up a VoIP network infrastructure over broadband Internet similar to setting it up at WAN level in organizations?
The answer to this really depends on the organization and their goals. If the organization deems that a best effort connection over the Internet is acceptable for their business, they can connect over a standard broadband Internet connection to make a WAN. Many businesses do this and the call quality is typically good in most cases. Even with some delays or occasional lost packets, most devices provide relatively decent quality speech due to jitter buffering and packet loss concealment algorithms. Many companies do build a VPN between sites over the broadband connection so they can share data securely. Most companies then route their voice calls through that VPN.
If a better guarantee of quality of service is needed for a business, the business should go to a provider that can tie multiple offices together and provide a service level agreement (SLA). One example of such a provider is Straitshot.