You'll need to own the games on Steam in order to play the remasters because they're essentially mods of those versions, but if you do then they'll be completely free. Now it appears that it's going to be those games, along with Tomb Raider 3, to PC. The classics will benefit of a new 3D engine, thus obtaining improved lighting and shadow effects, as well as advanced post-processing filters. You can see the tweet below.
With all the hype surrounding the newest Tomb Raider movie, it seems now is the ideal time to capitalize on the success, remastering the first three games for PC via Steam.
All the remasters of the game also fully support the Xbox 360/Xbox One controller, including the Unfinished Business & The Golden Mask DLC and integrate multiple fixes. And Realtech VR looks to take advantage, by bringing back some of Lara Croft's greatest adventures for a new audience to enjoy. Basically the remasters will use the original games' install packages, and that is why the remasters will only be available on Steam, too. Realtech VR has confirmed that the games will require the purchase of the DOS version being sold on Steam, just like ZDoom for playing the DOOM titles. Also the PC version will supports OpenVR and features a new 3D engine for both 3 games.
That means that Tomb Raider I, II, and III are all planned for free for all those who have previously purchased the titles. "Since TR classic is on Steam, we will use the game data from there".