This particular post has a lot to do with the multiplayer:

Serving All Your Supernatural Elimination Needs
For Ghostbusters Multiplayer we wanted to include featured locations from the Single Player game, but adapt them for Multiplayer use. All of the maps are designed to suit a majority of job types; it was critical that we allowed enough space for more enemies, more players, and more action! Threewave has some of the best level designers in the business and their expertise was critical in this regard.

Refining the different Job types took a long time. We had a good idea of how we wanted each to play but since we had no real network code for several months, our prototypes changed a lot over time. Once we were able to test the different Jobs, we quickly iterated on the rules and came to some solid decisions on what we felt was the most fun.

We also soon discovered we needed a few extra things to keep players challenged in Co-op Multiplayer as compared to the single player game. Four “live” Ghostbusters ended up completely destroying the AI ghosts! Teamwork was something we needed to focus on; in the Single Player game the other Ghostbusters help you, we wanted to make sure players did better by working together in Multiplayer.

Over the course of prototyping and development we decided to introduce limited ammunition and powerups; this choice really allowed us to reward teamwork and create some unique Multiplayer “Ghostbusters” technology items, such as the Proton Accelerator and the Ghost Shrinker.

We also added some unique Multiplayer AI “aggro” behaviours to challenge players even more. Some of these include ghosts that go berserk or even split in two when angered.

Persistent online ranking, automatic difficulty scaling and Most Wanted Ghosts to find and catch were added to keep players coming back to play again and again.

In Ghostbusters, ghost wrangling and trapping is one of the key elements players do over and over. The first time we tried Multiplayer wrangling, we knew we were on to something fun. In the Single Player game, if there are more AI players holding a ghost, the less the ghost struggles. We emphasized and added to this feature for Multiplayer Ghost Wrangling. If players work together, ghosts go down faster, and everyone gets a better score.

Check out the full post at IGN.com.