VERIFIED.
# rpm -q spacewalk-proxy-installer
spacewalk-proxy-installer-2.0.1-2.el6sat.noarch

#  grep -e rhn_parent -e http_proxy /etc/rhn/rhn.conf 
proxy.http_proxy = localhost:3128
proxy.http_proxy_username = user
proxy.http_proxy_password = pass
proxy.rhn_parent = xmlrpc.rhn.redhat.com

# rhn-proxy-activate --help
Usage: rhn-proxy-activate [options]

Options:
  -s SERVER, --server=SERVER
                        alternative server hostname to connect to, default is
                        'xmlrpc.rhn.redhat.com'
  --http-proxy=HTTP_PROXY
                        alternative HTTP proxy to connect to (HOSTNAME:PORT),
                        default is ''
  --http-proxy-username=HTTP_PROXY_USERNAME
                        alternative HTTP proxy usename, default is ''
  --http-proxy-password=HTTP_PROXY_PASSWORD
                        alternative HTTP proxy password, default is ''
  --ca-cert=CA_CERT     alternative SSL certificate to use, default is ''
  --no-ssl              turn off SSL (not advisable), default is on.
  --version=VERSION     which X.Y version of the Spacewalk Proxy are you
                        upgrading to? Default is your current proxy version
                        (5.2)
  -m, --enable-monitoring
                        enable MonitoringScout on this proxy.
  --deactivate          deactivate proxy, if already activated
  -l, --list-available-versions
                        print list of versions available to this system
  --non-interactive     non-interactive mode
  -q, --quiet           quiet non-interactive mode.
  -h, --help            show this help message and exit

# rhn-proxy-activate --version=5.6

--server (RHN parent):  xmlrpc.rhn.redhat.com
--http-proxy:           
--http-proxy-username:  
--http-proxy-password:  
--ca-cert:              
--no-ssl:               false
--version:              5.6

Are you sure about these options? y/n: y
Spacewalk Proxy successfully deactivated.
Spacewalk Proxy successfully activated.

>>> only rhn_parent is parsed as SERVER
>>> still http_proxy options need to be done too ( different bz )

Oops, step #2 in comment#2 has to be:

#  grep -e serverURL= -e httpProxy= -e sslCACert= /etc/sysconfig/rhn/up2date
serverURL=https://xmlrpc.rhn.redhat.com/XMLRPC
sslCACert=/usr/share/rhn/RHNS-CA-CERT
httpProxy=squid.redhat.com:3128



Anyway this fix introduced more mess into parsing options during proxy activation/recativation and the solution should be more complex considering rhn.conf file presence. (reactivation)

see bz #1010956

I'm sceptical whether the parsing of up2date is needed at all during 1st proxy activation (rhn.conf not present).

up2date file is parsed by configure-proxy.sh install script anyway and rhn-proxy-activate is run within using parsed options. No need for rhn-proxy-activate to parse up2date options itself. 

During reactivation only rhn.conf file matters, don't mess with up2date.

Red Hat Satellite Proxy 5.6 has been released. This bug tracked under Proxy. 

This bug either was VERIFIED or RELEASE_PENDING (re-verified prior shortly
before release). 

Moving to CLOSED CURRENT_RELEASE. 

Text from Upgrade Erratum follows:



Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

http://rhn.redhat.com/errata/RHEA-2013-1392.html