The short answer is YES, you can.
Although, a Toll-Free number is considered Inbound-only (meaning it is only to accept calls and not generate outbound calls). This distinction is important for a few telecom properties concerning outbound calls. However, in the case of E911, any calls to 911 will connect.
IMPORTANT: The FCC requires that providers of interconnected VoIP telephone services using the Public Switched Telephone Network (PSTN) meet Enhanced 911 (E911) obligations. E911 systems automatically provide to emergency service personnel a 911 caller's call back number and, in most cases, location information.
E911 is a service Flowroute provides to our customers as a way to connect to Emergency Services. The E911 service provided is within compliance regulations. As such E911 collects and assesses the location based on preconditioned DID Caller ID within which they store the customer's information provided to Flowroute by the customer.