Regional banks have a sufficient capital buffer to absorb the impact from the alternative capital treatment for securitisation outlined by APRA last week, Moody's says in a new report.  The impact would be to the tune of up to 0.5 percentage points in tier-one and total capital ratios. The tier-one ratios of regional banks already exceed 8.5 per cent, which Moody's judges a sufficient buffer.New rules on the retention of a subordinated tranche of a securitisation financing was already factored into bank ratings, Moody's said.Over the second half of 2010, APRA reviewed the bank practices under which the originating institution retained all or nearly all of the most junior tranches in a securitisation and, in the process, failed to transfer significant credit risk.ADIs that retain junior tranches will now be allowed to deduct holdings of junior tranches from capital, APRA said.Such holdings would be capped at the dollar amount of total capital that would be required if the entire pool had never been securitised. From this, ADIs can then make deductions as and when they sell the subordinated tranches.