No: You can't refinance if there is no equity. In your scenario, you're probably $30,000 or so under water.
No: You can't depend on a tax assessment to reflect the value of the property. It doesn't.
A Realtor could run a CMA and give you a pretty good idea of what your property really is worth. But it's a near-certainty that it isn't worth enough--having enough equity--for you to be able to refinance.
Hope that helps.