It's the very first words of the article.
Finally, this hour, a Chinese company has signed onto carve a canal across Nicaragua creating an alternative to the Panama Canal.
I think "sign" here means to make an agreement with another, right? But I feel somewhat odd about the word "onto". I don't encounter the word too much comparing to "to". So there any difference if I change "onto" to "to" here?
Is "carve a canal" a habitual expression? From the dictionary, I know that carve means to make an object or pattern by cutting a piece of wood or stone, using it in a canal makes me feel strange, how about dig a canal?