HS2 management suspends work at the majority of the sites with the exception of 5 sites considered curicial to the project. Some West Midlands sites are among the ones where the activities will continue. For other sites, no date has been given for the resumption of the activities.

The website of HS2 (https://www.hs2.org.uk/) has this banner (i made it italic):

In line with Government advice HS2 Ltd and our contractors have temporarily closed many of our offices and suspended works at a number of our sites.
The HS2 Helpdesk remains operational all day, every day, and is your first point of contact: Freephone 08081 434 434; Minicom 08081 456 472; Email: HS2enquiries@hs2.org.uk. If you contact us by post there will be an extended delay in us receiving and responding.

I was not able to find a detailed list other than what is published at https://www.expressandstar.com/news/local-hubs/staffordshire/2020/03/27/hs2-work-to-press-on-during-coronavirus-lockdown/

map image by User:Cnbrb / CC BY-SA