Hi,
you can forward these signals over the FPGA to you custom carrier if you have free IOs available.. But PHY LED Pins from Marvell ETH PHY are configurable, so how it works depends on the drivers and you check Marvell PHY datasheet how it should be configured and connected correctly. On the most carrier we use this LEDs simple as user LED, so it's not designed for ETH usage.
br
John