bus line vs transit line

bus line and transit line both are nouns.

Word	Noun	Adjective	Verb	Adverb
bus line	Yes	No	No	No
transit line	Yes	No	No	No

As nouns, transit line is a hypernym of bus line; that is, transit line is a word with a broader meaning than bus line:

bus line: an organization responsible for operating a bus transportation system
transit line: a line providing public transit

bus line (noun)	transit line (noun)
an organization responsible for operating a bus transportation system	a line providing public transit