Is it 'Made in Tibet?' or 'Made in China'?
According to this article from the Times of Israel
Yuval Steinitz, the Minister for National Infrastructure, Energy and Water Resources, and a close ally of Prime Minister Benjamin Netanyahu, accused the EU of unfairly singling out Israel when it has not taken similar action toward products made in areas like Chinese-controlled Tibet or Turkish-occupied northern Cyprus.
Although this may only apply for the EU, it shows that, at least in Europe, products produced in Tibet are not labeled as 'Made in Tibet'.
Another confirmation of this can be seen here
When it comes to China, the EU trips over itself to facilitate trade. As stated on the EU website on trade: “China is the EU’s biggest source of imports by far, and has also become one of the EU’s fastest growing export markets. The EU has also become China’s biggest source of imports. China and Europe now trade well over €1 billion a day.” Trade includes items made in Tibet, and the EU has not addressed any specific “Made in Tibet” labelling.
Both of these sources are related to the recent requirements imposed by the EU for labeling products produced in the West Bank and are not directly about Tibetan products.
At the same time, this Google search shows that there are products labeled as 'Made in Tibet' on the market, so it appears that 'Made in China' is the most common label, although 'Made in Tibet' is a possibility. It is not, however, required.