Roy pointed out to me in email that the highpass versions have a
positive phase shift, which is different behavior than a transmission
line. However, they do have the characteristic that they reflect an
open circuit as a short, and a short as an open, and an Ro load as Ro,
which is the behavior you want for the PIN switch. The phase shift in
that application should not be important. In general, both the pi and
T versions, and for both highpass and lowpass configuration, reflect a
load Z as (Ro^2)/Z, I believe, where Ro is the reactance of each
component.

Cheers,
Tom