Raspberry Pi IR blaster and Roomba IR codes

When I finally bought an iRobot vacuum cleaner, I went for the Roomba 620 which is the current entry model. This version doesn't come with any accessories like the "Virtual Walls" (infrared barriers), an infrared remote control, or handy features like scheduling.

However, all of the above ought in principle to be possible by transmitting infrared (IR) signals from a DIY circuit... or a Raspberry Pi? For example, with older model Roombas people have used LIRC and an IR Blaster to tell their Roomba to start cleaning by mimicking the remote control - with the computer handling the scheduling.

Raspberry Pi Infrared Blaster,
using a P2N2222A NPN transistor,
and two IR LEDs in series with 3.3V

Roomba 620 infrared signals

Having been pondering it for a while, I recently bought an iRobot Roomba vacuum cleaner - the Roomba 620 which is the current entry model. For fun I took some photos with an infrared sensitive webcam (a trusty XBox Live Vision), and then measured some of the IR signal codes with my Raspberry Pi.

Note the four downward facing IR LEDs (cliff sensors)

Does the Roomba use IR illumination to follow walls?