It is a big deal, but they aren't splitting their class A shares. Class B was introduced to make shares more affordable to people who wanted to invest, but wanted a lower entry point. I think splitting the B stock is keeping with that sentiment.
I believe Class B wasn't introduced for that reason, if I remember correctly it had something to do with people with Class A needing to divide stock to leave it in their will or as gifts.
The split won't actually raise capital for the deal, but will help to payoff shareholders of the railroad. According to http://www.marketwatch.com/story/berkshire-approves-50-for-1... the split is to "accommodate holders of smaller amounts of BNSF shares who opt for a share exchange rather than a cash payment."
So, some shareholders of Burlington will opt for shares instead of cash, and since you can’t own a fraction of a share, they have to split the stock to accommodate them.
Wow Buffett splitting stock?!
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