Does the Dieckmann Reaction proceed via the conjugated enolate of the product?
The first four steps (i.e. the main reaction) are conducted under basic conditions due to the presence of alkoxide. When that reaction is complete, the result is the deprotonated ketoester--the formation of that stable species is what drives the reaction to completion. Note that the first 3 steps are shown as equilibria, whereas the fourth step is essentially irreversible. 

Later, during workup (shown above as the fifth step of the process), acid is added to neutralize that anion and form the final product.