The opening tunnels just after the lift are directly modeled after HL1 (with the exception of the office at the bottom, that’s new). The ramp room also comes from HL1, although it is definitely expanded. The houndeye landing is mostly captured too (although it’s a dead end in the stock version and you can’t take your tram there).
In place of the crane is the electrical pool puzzle, which is completely new to Black Mesa. And the turret elevator is a stand-in for the marine elevator in HL1’s version. Both are present in On a Rail Uncut, with the former a full recreation and the latter as a sort of nod.
If you want to count the Loop Mod version of the opening map, you also get the box track (which comes after the ramp room in the original), as well as the pipe bridge room. The security office area does not have a HL1 counterpart.