Regarding the PepsiCo move, I have a little in depth knowledge of their reasoning.
Pepsi had quite a long term lease at 555 West Monroe (currently been there since 2002 when the building was built), well below market rent, and until recently, leased the entirety of the building. As the lease came closer to expiring, senior leadership didn't have a cohesive plan about future space needs at the building, or Chicago in general. Numerous layoffs within the building have
dramatically cut the need for space and I believe their short term plans are to only occupy half of the building at most, which jives with what Crain's has. (~230K sq ft)
All of the buildings close to Union and Ogilvy have seen their rents increase materially over the past 10 years. Pepsi didn't want to absorb that increase, especially given the business units that operate in Chicago are not performing well financially. My guess is that the OPO offered something slightly (or even well) below market to get Pepsi to jump.
Perhaps the OPO is offering all of these companies something below market rate to get them in the door, knowing that large tenants like this are less likely to move than smaller firms when rates increase in the future?