Um, this is not what IBIS is for. IBIS ("I/O Buffer Information
Specification") is used to describe active circuits, where SPICE
structural models reveal too much information which might be
proprietary. IBIS models are generally 1-ports (loads, outputs).
Me thinks you should be asking for a SPICE model; and because all but
the simplest of t-line implementations differ among SPICE (and
SPICE-like) vendors, you might want to specify which simulator you
plan to use this with, among other things.