Here is what the proposed regulations says about your question: (viii) Real property straddling a qualified opportunity zone. For purposes of satisfying the requirements in this paragraph (d)(5), when it is necessary to determine whether a qualified opportunity zone is the location of services, tangible property, or business functions, section 1397C(f) applies (substituting “Qualified Opportunity Zone” for “empowerment zone”). If the amount of real property based on square footage located within the Qualified Opportunity Zone is substantial as compared to the amount of real property based on square footage outside of the Qualified Opportunity Zone, and the real property outside of the Qualified Opportunity Zone is contiguous to part or all of the real property located inside the Qualified Opportunity Zone, then all of the property is deemed to be located within a Qualified Opportunity Zone.