Connecting two Ethernet PHY without magnetics?
You might be interested by these Application Notes about transformerless/magnetic-less ethernet application


Intel AP-438 : http://www.intel.com/content/dam/doc/application-note/8255x-fast-ethernet-controllers-without-magnetics-appl-note.pdf
TI AN-1519 : http://www.ti.com/lit/an/snla088a/snla088a.pdf


They both have an example of transformerless operation on a PCB, with a capacitor in place of a transformer.
In a case where you control both side of the connector, only one capacitor on the line can be mounted. But if you control only one side you have to put a capacitor two, in case the other side has nothing or has a transformer.

I had to work on a 1000Base-KX backplane connection, and its problem is this standard is not very well known and you can have difficulties to implement it, have information about it, etc.

In my case I needed to have an oscilloscope pattern to observe the signal. After few email to the oscilloscope company and few phone calls I had them understood that I was talking about 1000Base-KX and not 1000Base-CX (Ethernet over Coax).

The 1000Base-KX was "retro-implemented" in the IEEE802.3 when the 10GBase-KX was created. So the 1000Base-KX is a standard derived from 10G and officially become a IEEE standard years after the adoption of the Gigabit standards.

Also 1000Base-KX only need 2 pairs (Full-Duplex) but the operating frequency is around 1Ghz which involves signal integrity issues where 1000Base-T and 100Base-T(X) stays at 125MHz.