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My plan since getting the CSP a year ago was to close the card before the AF hits and move the limit into my Freedom. This was rumored to be possible (and I recall confirmed through the personal experiences of some members), but I haven't tried it yet. I'm hoping that this is/has been possible for selfish reasons.
Yes you can consolidate limits with chaes co-branded or not.
Not sure of a starting point...but last month (Feb 2015), after having cards for only 3 months, I transferred $3,000 of $3,500 Chase Amtrak CL to Chase SW CL - now SW is $7500 and Amtrak is $500.
Only keeping Amtrak for rewards and son's use when off to Duke Univ (east coast) next year, and after getting free Amtrak Tix from Duke to WA DC for our trip in a couple of weeks...saved $160 in tix.