What is Mobility?

Mobility is the ability of a CPA or CPA Firm who has a current/active license from a state that has passed Mobility Legislation, or for a CPA with individual substantial equivalency, to gain a practice privilege in Florida without having to get an addition license in order to serve a client.
References:

How do I know if my state is substantially equivalent?

The list of substantially equivalent states is available below:

CPAs & Mobility – Substantially Equivalent States (Revised August 15, 2014)

Incorporated by Rule 61H1-29.002, Florida Administrative Code

An active licensed CPA in good standing who does not have an office, pursuant to section  473.3141(1)(a), Florida Statutes and defined by Rule 61H1-20.001(8) Florida Administrative Code, could practice in Florida without notification or fee. The following states are considered substantially equivalent:

Alabama* Alaska Arizona Arkansas California Colorado
CNMI Connecticut Delaware District of Columbia   Georgia Guam
Hawaii* Idaho Illinois* Indiana Iowa Kansas*
Kentucky Louisiana Maine* Maryland Massachusetts Michigan
Minnesota Mississippi Missouri Montana* Nebraska* Nevada
New Hampshire  New Jersey New Mexico New York North Carolina North Dakota
Ohio Oklahoma* Oregon Pennsylvania Puerto Rico Rhode Island
South Carolina South Dakota Tennessee Texas Utah Vermont
Virginia Washington West Virginia   Wisconsin Wyoming

*These are two-tier states. The first tier is examination; a certificate is issued when an applicant passes the examination, which does not allow the individual to practice as a CPA in their home state nor does it allow the individual to practice in Florida. The second tier is licensure; only those individuals who hold an active license to practice in their home state are eligible to practice in Florida without Florida licensure, pursuant to section 473.3141(1)(a), Florida Statutes.

The following jurisdiction has been found to not be substantially equivalent and individuals would need to obtain verification from the Florida Board pursuant to section 473.3141(1)(b), Florida Statutes that their personal qualifications are substantially equivalent to the certificate required in Section 5 of the Uniform Accountancy Act in the issuance of licenses.

Virgin Islands

If my state of licensure has Mobility of if the Florida Board of Accountancy determines that I meet the Mobility criteria set forth in section 5 of the Uniform Accountancy Act, is there any circumstance that would still require me to get a license?

Yes. An individual may only perform the services outlines in s. 473.302(8)(a), F.S. through a  license firm.
References:

cpaverify
cpamobility