Standard verb collocation.
开 ('to open / run') +
直通车 (Taobao's CPC ad product). Note
开 here is the same generic 'to operate' sense as in
开店 (run a shop) or
开车 (drive a car), neatly punning on the literal 'open the train' reading. Taobao sellers who
开直通车 are essentially buying their way into the search results.
