Search:

I think one could hear that if it was implied by context that the speaker was talking about tractors compared to "enough" of something else.
But I would guess that you are right in principle, and...

I think of it it like this.

I will use "of" if the thing I am talking about are many or it is one out of many.

There are not enough of these.
There are not enough of these tractors.
There...

I don't think "of" should be there either.[/quote]You're probably right. Perhaps I lived in the USA for too long.

I would say, "There are not enough of facilities such as these."