Hi...
as the same behavioral/naer to accurate...transistors will using by replace what ever u need...means...if u want to use transistor in design..but not available in library...then u will mapping the transistor as related behavior trans...
For a better understanding ... try reading "Art of Analog Layout" - by Haskins ... you will find what you need and more in chapter 12 section 4. Best of luck
if transistors are working at higher frequency then the characteristics of adjacent trans will change, to avoid this we provide same environment to a critical transistor i think this is called macthing