Yes, that's one of the most prominent in a long line of attempts at creating formal models of OOP. And in the preface, you'll find:

> There is a well-established theory of functions, the λ-calculus, ... However, our theory of objects is self-contained; it is the first that does not require explicit reference to functions or procedures.

So that answers your question in the negative and proves my point: no, not every language is based on lambda calculus.