As you may know an ETF (Exchange Traded Fund) must track a registered index (you can read my post on ETFs and ETNs for more information). Many exchange traded funds follow a Lehman Brothers Index. Barclays is buying many of Lehman Brothers’ assets, including their name, New York Building, trading, risk management, and index departments; they will be giving all 10,000 Lehman employees a 90 day contract to choose the best fit employees, laying off the rest. It is unclear what exactly Barclays will do but Barclays has been given special promission to provide an index to an ETF it issues. Ussually an index provider must be a third party to an ETF provider. Read more about this Here
Even if Barclays did not buy Lehman’s index department the assets held in trust by the ETF are safe and there is no risk of default or loss. Since the index an ETF tracks is just a set of rules and guidelines in which an ETF most follow for investment. This is why ETFs are called passive investing. Worse case the ETF would have to adjust to a similiar but different index. This may cause some assets and allocations to change but it would not have any tax consequnces.
Barclays will not however being buying Lehman Brothers strutured debt including their ETNs (again read my blog on ETNs to get up to date with their unique risks). This promisory notes that Lehman has will most likely default. These ETNs include EOH (Opta Lehman Commodity Pure Beta Agrowculture) and RAW (Opta Lehman Commodity Pure Beta). Read more Here
Also, AIG acts as an insurance provider for some large european ETC issuers (ETCs are Exchange Traded Commodities pretty much just like an ETN). This large issuers have credit agreements with AIG which insures their ETCs in case of default, these are a form of credit swaps. Read More Here