The commissioning of the Russiagate ICA was announced at a breakfast on the morning of December 9, 2016 by Lisa Monaco. It had been commissioned on December 6, 2016 - see link.
ICA series: Part 1; Part 2; Part 3
The announcement was promptly reported in US media: WaPo, NYT, CNN, Politico.[1]
Press liaisons throughout the intel community were equipped with talking points that are documented in ODNI emails[2]. Among the recipients were Ned Price EOP/NSC, Mark Stroh EOP/NSC, John Kirby (State), Mark Toner (State), Elizabeth Trudeau (State), Marc Raimondi (EOP/NSC), Timothy Barrett, Michael Birmingham.
In a follow-up story, Nakashima and Entous reported[3] that the initiative arose due to a supposed “clamor from Democrats and some Republicans”:
The clamor from Democrats and some Republicans for a more fulsome accounting prompted the White House on Friday [December 9, 2016] to announce that President Obama had ordered a full review of Russian cyber actions during the 2016 campaign.
In context, the so-called “clamor” was almost certainly the November 30, 2016 request by SSCI Democrats for public disclosure of the contents of the November 29, 2016 SSCI briefing by CIA about the new “information” that Putin preferred Trump. The result was the commissioning of a CIA-led assessment that would leave a “permanent” and public stain on the incoming Trump administration.
ICA series: Part 1; Part 2; Part 3; Part 4
[2] Jason Leopold, Buzzfeed, FOIA, Nov 9, 2018. https://s3.documentcloud.org/documents/5031716/LEOPOLD-SHAPIRO-ODNI-FOIA-RUSSIA-HACKING.pdf
[3] Entous and Nakashima, Dec 10, 2016.. https://www.washingtonpost.com/world/national-security/fbi-and-cia-give-differing-accounts-to-lawmakers-on-russias-motives-in-2016-hacks/2016/12/10/c6dfadfa-bef0-11e6-94ac-3d324840106c_story.html