premise: If the cost of the PP and E acquired equals the book value of the PP and E surrendered, there is no gain or loss (nor a revenue or other financing source), because the exchange of one asset for another of equal value does not provide a net inflow of resources.
hypothesis: PP and E acquired cost equals book value of PP and E surrendered; therefore, there isn't a gain or a loss because there's no net inflow of resources with exchanging assets for another one of the same value.