Even without the agreement the B1G already plays quite a few Pac-12 teams and with the Rose Bowl a pact may not be necessary. Since 2000 the Big Ten has played 69 total games against the PAC 12, 52 against the Big XII (NU excluded), 45 v. the SEC, 36 v. the ACC, and 35 v. the Big East.
Just last year;
Ohio State v. Colorado
Wisconsin v. Oregon State
Minnesota @ Southern Cal
Nebraska v. Warshington
Illinois v. Arizona State
2010:
Minnesota v. Southern Cal
Iowa v. Arizona
Wisconsin v. Arizona State
and next year,
Wisconsin @ Oregon State
Ohio State v. California
Illinois @ Arizona State
Nebraska @ UCLA
future matchups;
2013
Illinois v. Warshington
Northwestern @ California
Wisconsin @ Arizona State
2014
Illinois @ Warshington
Michigan v. Utah
Michigan State @ Oregon
Northwestern v. California
Wisconsin @ Warshington State
2015
Michigan @ Utah
Michigan v. Oregon State
Michigan State v. Oregon
Northwestern v. Stanford
Wisconsin v. Warshington State
2016
Michigan v. Colorado
Northwestern @ Stanford
2017
Minnesota v. Oregon State
Wisconsin v. Warshington
2018
Minnesota @ Oregon State
Wisconsin @ Warshington
2019
Northwestern v. Stanford
2020
Northwestern @ Stanford
2021
Minnesota @ Colorado
Northwestern v Stanford
2022
Minnesota v. Colorado
Northwestern @ Stanford