I spent too much time researching this last night, I can't stand a research project that doesn't reach a conclusion.
It's on the State, with 80% confidence.
Interstates are owned by the States in which they are located. Originally there was a 50% Federal match for cost, that has now risen to 90%, but States retain ownership of the roads. "Interstate" is a designation, not ownership.
https://www.fhwa.dot.gov/interstate/faq.cfm#question5This means the interchanges in question would be on the State. But the State can have whatever mechanisms in place it wants, so it could delegate to the City or County under Federal Law. BUT - I don't see anything in Oklahoma that does that. Also, ODOT advises of ramp closures and maitnenance on their website... which could just be helpful, but also indicates they are the ones doing the work since they indicate when the work will be done:
https://www.ok.gov/odot/Tulsa_Metro_Construction.html Now, if you want a NEW interchange - ODOT can make you pay for it. See, .e.g., Jenks buying a new interchange for Simon's new strip mall.
ODOT Spec Book
http://www.okladot.state.ok.us/c_manuals/specbook/oe_ss_2009.pdfODOT Tulsa map
http://www.odot.org/maps/state/2015/map_state_2015_inset-tulsa.pdf