It turns out that, despite media reports to the contrary, Bishop Laun did not excommunicate anybody. The story actually comes from a German-language interview on Kath.net (English translation provided by The Cafeteria is Closed) in which Bishop Laun's opinion was asked as to whether the landlord in question has excommunicated himself. This statement is a far cry from the legal process by which ordinaries can impose/declare penalties. See 1983 CIC cann. 1341–1353.
Thus, it seems it is a purely academic discussion and not a formal process to penalize anyone. Well, how about we take the academic discussion slightly further.
Could the landlord be considered an accomplice within the meaning of can. 1329, and thus incur the same penalty?
Maybe. The requirement for whether he would be considered an accomplice would be whether he conspired together with those who procure abortions to commit an offense. Id. can. 1329 § 1. It sounds like this would apply here. Since the penalty for procuring an abortion is an automatic censure though, id. can. 1398, the only way the landlord would be liable for the same automatic penalty if he were an accomplice would be if without [his] assistance, the crime would not have been committed, and if the penalty is of such a nature as to be able to affect [him]
, id. can. 1329 § 2. I am not sure as to whether this would be applicable. The second part of this criterion is easy: as a Catholic, he can receive an excommunication, so the penalty is able to affect him. The first part is trickier. On first look it would seem that without the landlord's help abortions would not be procured. However, penal laws require strict interpretation, and Jimmy Akin, applying strict interpretation, argues that the landlord is not an essential accomplice.
Regardless of whether the landlord is an essential acccomplice, he would still only be liable for the automatic excommunication once the actual delict (procuring an abortion) actually occurs. This is just a matter of time, though, once the clinic opens. Even if Jimmy Akin is right (as I suspect he is) and it turns out that the landlord is not essential in the procurement of the abortions at this clinic and thus is not liable for the automatic censure, he can definitely receive imposed censures if he were actually a non-essential accomplice. Id. § 1. This is, of course, assuming that he is indeed an accomplice under the law, because he might not be.
How about Bishop Laun imposing a penal precept on the landlord?
Assuming that Bishop Laun has ordinary executive power in this case (my previous post went over the necessary conditions), he should also be able to impose penal precepts. He has already argued that the divine law is the law in question here (citing the Catechism), and precepts can be used to enforce divine law that does not already have a penalty prescribed by ecclesiastical law. He still probably could not prescribe an automatic penalty for a precept of this kind since the presence of malice is questionable, but he definitely could prescribe a normal penalty, including a censure.