It depends where the "métro" is located. If it Paris, Montreal, Newcastle etc. then it should be called a metro. If it is London, then call it the Underground with a capital "U", but not the "Underground Railway" unless you are trying to use a 19th century form of words.

On the other hand, as can be seen from the ref. below, (see photo on website), it is just possible that they mean the fancy wrought ironwork at the entrance to the metro. The English translation of this website is dreadful - in spite of Canada being ostensibly bilingual - and doesn't translate this extract.

"Un monument à l’effigie de la reine Victoria d’Angleterre est érigé au centre du square nommé en son honneur. Moins d’un siècle plus tard, une authentique grille de métro parisien, œuvre de style art nouveau, viendra orner l’entrée de la station du même nom."
http://www.tourisme-montreal.org/Discover-montreal/Itinerari...



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Note added at 1 hr (2010-05-04 15:33:05 GMT)
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"Cross section of shelter and Underground platforms at Goodge Street ... a ventilation grille on the west bound Piccadilly Line platform. ..."
underground-history.co.uk/shelters.php -

"Created in the 1900s, the new Underground lines created by Charles Yerkes ... This ventilation grille, taken from Hampstead station, would have been used to ..."
www.20thcenturylondon.org.uk/server.php?