Can you purchase or can you use Travel Tickets (particularly boat tickets) in the Dreamlands?

There are locations connected by Ship paths, so yes you can use boat tickets (thematically.... yoh I dunno, you prepared for your travels mentally... if by water)

Answered on your other question too, this link might be useful:

https://rpggeek.com/thread/1676463/preview-new-ancient-ones

The key at the bottom of the map is what I have based my two answers on.

You should be able to acquire boat tickets on City spaces in the Dreamlands that have a Ship path connected to them (classic rules)

Lore-wise, items which exist in the current world transform into fantasy equivalents in the Dreamlands. A gun might become a crossbow, a motorbike might become a horse, a typewriter would be a stack of papers and a quill, etc. In such a light, it wouldn't be too hard to imagine that a travel ticket for the Lusitania becomes a promisary note to be exchanged for passage on a merchant ship.

Then how does a promissory note become a Lusitania ticket when I awake?

Lore-wise, items which exist in the current world transform into fantasy equivalents in the Dreamlands. A gun might become a crossbow, a motorbike might become a horse, a typewriter would be a stack of papers and a quill, etc. In such a light, it wouldn't be too hard to imagine that a travel ticket for the Lusitania becomes a promisary note to be exchanged for passage on a merchant ship.

Legit