Yes, you can use locomotives to replace any of the coloured cards on a route, even if it has ferries.
Locomotives are multi-colored, and act as wild cards in the game.
Locomotive cards can be played along with any set of cards when claiming a route.
On any route, the "usual set" of coloured cards includes possible use of locomotives.
I've been doing some research to see how Marklin, Deutschland, and Germany differ. Here's what I've found so far for sure.
Marklin vs. Deutschland vs. Germany.
Marklin came out first and had the most complex rules of the three. It was a Limited Edition Special Release product which covered the map of Germany released in 2006. Deutschland came out as the ...
I tried this myself and came out with a very similar solution to Etiën Alssema's answer. It eeks out a few extra points. It scores 248 without counting the longest track.
There is a continuous track 33 pieces long from Brest to Sofia.
Train stations borrow red's tracks:
Budapest - Kyïv - Smolensk
Palermo - Roma
Remaining train ...