RC pulldown on the MDI lines between the ethernet PHY and RJ45 Connector
This setup allows for a 100 ohm differential termination and a 50 ohm termination at higher frequencies for the ustrip/strip lines that the differential traces will likely be laid out with.  the net DC term across the differential traces will not be zero but will be midrail.

The differential amplifiers inside the IC all have CMFB (common mode feedback) amplifiers so the capacitors help hold this value and stabilize the DC value, they would of course need to be designed with these caps in mind but the 47 ohms does help ensure the phase margin is met.

The draw back of course is that there is now a RC time constant associated with the CMFB and the common mode level.

It is likely that these measures all help ensure a larger eye opening.