XtremIO 10GBe iSCSI port question

Hello, I have a customer looking at a 10TB X-Brick for their disaster recovery environment. They already have XtremIO in their production environment and are looking to have a duplicate infrastructure for DR . The issue/question is their current network infrastructure at their disaster recovery site is only 1GBe and they don't plan on upgrading to 10GBe until Q4 this year. Can they use the 10GBe iSCSI ports on the X-brick with the 1GBe network infrastructure? That is, will the 10GBe ports on the X-Brick downgrade to 1GBe? If so, is this a supported configuration from EMC? 

They don't have the option for FC as they don't currently have a fabric in DR

I know going to 1GBe is counter intuitive to the performance benefits of XtremIO but this is a bit of an odd case as my customer has budget for storage right now and will need to upgrade the network at the later date.

Thanks

DMH