You are asking the right questions. But, the answers are subjective.
Part of the answer is that prior to the recession a subsidiary of Lehman Brothers (Neuberger Berman) was actively accumulating shares in KCS. They became the largest shareholder owning approx 14% of the company.
One year ago last week Lehman Bros. was liquidated.
Similarly, there were two other hedge funds that were enhancing their holdings of KCS, probably with the view of orchestrating KCS as a takeover target. (Same thing was happening over at CSX with the TCI et al. hedge funds.)
The hedgies got caught and were forced to liquidate their positions. The larger railroads share prices were not "punished" as much because:
1. their ownership was less influenced by hedgies
2. they pay dividends
3. KCS is only starting to reap the benefits of a larger transportation franchise.
4. KCS bonds are not investment grade and so, with the deleveraging that took place, KCS was perceived to be potentially vulnerable.
5. the insecurity resultant from the backlash from the "buy American" source clause in the US stimulus package made KCS vulnerable because of their Mexican franchise.
6. a Democrat was elected President whereas the Governor and state of Texas is Republican--thereby likely stalling the development of the TransTexas Corridor and associated infrastructure funding.
Everybody will have opinions--all of which, like mine, are just "tea leaf reading", but, likely contributed.
beagle