The issue has to be fixed by Red Hat, they are the ones that created the problem they have to fix it we can't. you could package libtalloc2 to not conflict at all with rhel and allow rhels package to be installed and work fine. in the instance of rhel doing something that makes a package not work in epel and there is no way to package things so that they can all live happily and work we have to remove the package from epel and send an email to the announce list stating so and why. This is one of the pain points in having Red Hat go off and do its own thing and not considering us. we can only work as much magic as we can to make things work.
Well, in this particular instance, given that the two versions of the package had different sonames, I judged* that the rule of "Don't break existing deployments" was more important than the rule of "Don't upgrade RHEL packages" in this case. My EPEL package is bundling a compatible version of the older soname (built directly from the sources in the RHEL SRPM) so as to minimize the damage until RHEL 5.6 can sort this out properly.
In my opinion, taking this package out of EPEL (and all of its descendents, including SSSD which I am aware of being used by a number of very large deployments) would be far more disruptive than simply bending the "updating package" rule for a few months.
* This is not a decision I made without the input of many others on #fedora-devel
-- Stephen Gallagher RHCE 804006346421761 Delivering value year after year. Red Hat ranks #1 in value among software vendors. http://www.redhat.com/promo/vendor/