Trump Post Office Mechanic's Liens

It's not often that one finds mechanic's liens in the news.  I think this is ripe for inclusion in secured credit casebooks.

Update:  After thinking about this more, this gets more interesting than a plain vanilla mechanic's lien.  Recall that Trump doesn't own the Old Post Office.  He has a leasehold, and the building is owned by the federal government.  So this raises the question about whether the lien reaches to the fee simple ownership of the federal government or if it is a lien on the leasehold.  I have no idea. There are some states in which a mechanic's lien triggered by work done by a tenant reaches the landlord's fee simple ownership if the work was done with the landlord's consent (see here, e.g.). DC doesn't appear to have caselaw on this.  (If the lien is filed against the federal government itself, there's a different process through the Miller Act, but I doubt that applies since the federal government was probably not a party to the construction contract.) 

A potential further complication is the status of federal property in DC. Can it be subject to mechanic's liens?  Can it be foreclosed on?  Where does sovereign immunity come into play?  

Finally, what is the effect of a lien on the property on Trump's leasehold?  I can't imagine that there's any way to actually foreclose on Trump's leasehold--the lease for the Old Post Office isn't going to be freely transferable.  If so, what good does a mechanic's lien do, other than embarrass Trump?  Is it an Event of Default under the lease if Trump suffers it to persist?  If so, that would give the contractors some leverage, but this all seems much messier than a typical mechanic's lien situation. 

I'm somewhat perplexed.  Trump doesn't own the Old Post Office.  He has a leasehold.  So is the mechanic's lien filed against his leasehold or against the building?  I don't see what good it does to file it against a.  A mechanics lien gets paid in one of two ways.  Either it gets paid when the building is sold or it gets paid after foreclosure by the unpaid contractor following a successful suit for the unpaid balance.  Given that the building is federally owned, I'm not sure what either of this means.