I would say that procedural code is less inclined towards both immutability and encapsulation than OO; I would say to a first order approximation that it tends to be worse than OO for concurrency.

But there are moderating factors. Procedural programs that don't enforce strict modularity conventions tend to be bound in size by their complexity, a complexity that works against the level of understanding necessary to make things both concurrent and correct. Meanwhile, procedural programs that do enforce strict modularity will probably be using conventions that emulate a different paradigm, and will inherit that paradigms' costs and benefits WRT concurrency.