It's a strange turn of phrase, which is derived from a poem by the famous Scottish Poet Robert Burns:

But, Mousie, thou art no thy lane
In proving foresight may be vain:
The best laid schemes o' mice an' men
Gang aft a-gley,
An' lea'e us nought but grief an' pain,
For promised joy

I say strange because as in the poem it is generally used in the sense that the "best-laid plans gang aft a-gley", i.e. "the most carefully prepared plans may go wrong".

In this context, they have taken the original meaning and changed it somewhat, since here, as you suggest, it means plans that are well thought through and elaborated.

Shame the author did not know his Scottish history....