One could flag an appropriate question, then select "in need of moderator intervention", then type something like "should be migrated to opendata.stackexchange.com".
BTW, more than 35% of our tags have their "counterparts" on Stack Overflow. These tags are:
accelerometer, analysis, api, astronomy, audio, authenticity, bank,
bittorrent, calendar, categories, census, city, ckan, classification,
crowdsourcing, csv, data.gov, database, dbpedia, demographics,
dictionary, documentation, doi, download, economics, edgar, email,
energy, environment, excel, fasttext, finance, french, genome,
geocoding, geospatial, github, global, hadoop, html, irs, japanese,
json, kml, licensing, linked-data, longitudinal, machine-learning,
mapping, maps, media, medical, metadata, migration, mooc, music,
names, nlp, noaa, normalization, odata, ontology, openrefine,
openstreetmap, parking, parsing, pdf, photos, polling, population,
postal-code, privacy, products, publishing, pubmed, python, r, rdf,
real-time, reliability, rest, search-engine, security,
sentiment-analysis, shopping, social-media, socrata, space, sparql,
sql, standards, state, survey, text, time-series, traffic,
translation, trust, untagged, visualization, weather, wikidata,
wikimedia-commons, wikipedia, wiktionary, wkt, word2vec, wordnet, xml
out of topic
are often marked as too old to be migrated ... I can't provide an example because I didn't keep track of the link