Open Source for the Enterprise

I just posted a review of this recently-published book:
http://changingway.net/archives/230
I'd be interested in any views from members of this community on a question
in my mind (and in the review). There seems to be a tendency (not just in
this particular book) to say to IT managers: here's how you should evaluate
FLOSS for your organization. That's fine, but why not say: here's how you
evaluate software for your organization (or here's a model or two for doing
so); now let's see how FLOSS fits in to that model.
The contrast is between model-for-FLOSS and model-then-FLOSS ways of
getting at the subject. I think that Feller and Fitzgerald, in their book
on open source development, use the model-then-FLOSS approach effectively
(see ch. 4, in which they derive their framework for FLOSS development from
existing, more general and established frameworks for software
development).
I perceive a tendency for people writing about FLOSS deployment to take the
model-for-FLOSS approach. I have, I think, three questions:
1. Do others perceive the same tendency?
2. Can anyone explain it?
3. Are there any counter-examples, i.e., accounts of FLOSS deployment that
take the model-then-FLOSS approach?
Thanks for any thoughts,
Andrew