Is there a standard bandwidth equation for companies to use to identify the average bandwidth requirements for their employees? Example; I have a company with 50 employees. Will a single T1 provide the required bandwidth for our day to day operation?

Impossible to tell. Are your employees using email, the web, web apps, connecting to remote databases, streaming AV content, using VOIP? If they use email and occasional web use only then 1.544Mbps can support about 10 concurrent users before lag becomes an issue.