The name implies that these records are just for the crossing from Canada into Vermont but they are more expansive than that.
Many people passed through Canada in the mid and late 19th century, for these people there are no records. Many Europeans from Britain, Scandinavia, Northern Europe and Russia arrived during this time. As the US began to impose stringent rules on its ports of entry, many immigrants chose to go to Canada first and then pass easily into the United States across its open northern border.
In 1894 the US government was finally able to convince steamship companies in Canada to treat all passengers destined to the United States as if they would be landing at a U.S. port of entry. This meant completing a U.S. ship passenger manifest form and selling tickets only to those who appeared admissible under U.S. law. Canadian railroads agreed to carry only those immigrants who were legally admitted to the United States to U.S. destinations.
US Immigration Service had inspectors at Canadian ports of entry to collect the manifests and to inspect the immigrants who were bound for the United States.
Between 1895 and 1906 the US also put inspectors at northern land border crossings. People who arrived by boat received a certificate of admission which they had to present to the guards at the US border when their train was stopped. Before 1906, only foreign born immigrants are tracked but after that time also those born in Canada who were traveling to the United States.
If your ancestors came through Canada during this time period they should be in the records. The records were kept until 1956. Ancestry.com has records of Canadian border crossing from 1825-1960 and for Detroit until 1963. Records can also be found at Familysearch.org/