Hmm, could be. Seems thin, yet pretty hard. Could be consistent with a high-P electroless deposit?
Could definitely be oxidized too.
Bad pic:
You can't really tell the color because of the lighting, but in the area where I've scratched through, it looks coppery, and with not much scratching necessary. It did take some pressure to scratch through, otherwise the scraper just skated right across.
Exact part,
http://www.st.com/content/ccc/resource/technical/document/datasheet/07/2c/12/ed/d3/c2/42/99/CD00218149.pdf/files/CD00218149.pdf/jcr:content/translations/en.CD00218149.pdfbut they don't specify plating (at all, it would seem). A quick search doesn't suggest anyone is doing bare nickel (I saw one hit for IR's packaging: lead-free tin plate, nickel underplate).
Rather a lack of information...
Suffice it to say: it's up to you. If you have the parts, and they solder well -- or not -- that's that. Don't expect to be able to look it up in the datasheet, before ordering parts, or without looking at the parts in hand.
Tim