NEW DELHI, Jan. 17 -- The Tata Motors Ltd stock has been racing full throttle over the last few months. It rose 83% from its 52-week low in September, making it the best performer among automobile original equipment manufacturers in a year.

The moot point: Is this rally sustainable? Indeed, investors are optimistic that the worst is behind the firm. Headwinds in both domestic and global markets are receding.

The first flicker of hope came when the Brexit deal was inked. Investors were relieved as a no-deal Brexit would have meant uncertainty on customs duties between the UK and countries in the European Union (EU). Tata Motors' 100% subsidiary Jaguar Land Rover Ltd (JLR) gets one-fifth of its sales from the EU, besides importing parts fro...