Since Debian 8.0 is based on the 3.16 kernel, a lot of recent LIS features are built-in. We will be updating
https://technet.microsoft.com/en-us/library/dn614985.aspx to indicate which features are included soon, but for now the LIS features included should be equivalent to Ubuntu 14.10.
Booting a fresh Debian 8 on Hyper-V, I see the following modules when I lsmod: hv_utils, hv_netsc, hv_storvsc, hv_vmbus. Under vmbus you will even see the emulated graphics, keyboard, and mouse as hid_hyperv and hyperv_fb.
Integration features and improvements continue to be developed and integrated into a lot of Linux distributions, including Debian, and a lot of those features are coming from the upstream kernel.