[AT&T, Rogers HTC One X, Telstra One XL] dave-:
While we're talking about altering this already great ROM, might I suggest replacing ES File Manager in favour of say Solid Explorer which has a much nicer interface and is well suited to our large crisp display ;)

Sure thing. Have attached a zip (not flashable as I don't know how to do that) where I have kept the directory structure and just modified your original files. I also added an APK from our carrier which some people like for widgets (it has to be in /system/app). For reference, the changes I made are below :)

The only change which I couldn't figure out how or where to add is our APN's. Details are:

<apn carrier="Telstra Internet" mcc="505" mnc="01" apn="telstra.wap" type="default,supl" />
<apn carrier="Telstra MMS" mcc="505" mnc="01" apn="telstra.mms" mmsc="http://mmsc.telstra.com:8002" mmsproxy="10.1.1.180" mmsport="80" type="mms" />

customize/CID/default.xml

locale
device name

customize/MNS/default.xml

locale
time format
weather_provider cities and unit
stocks
added a bookmark, changed homepage and removed some
mail_signature
duplicated MessageConfig from stock
UA strings

build.prop

Basically modified or added to mimic stock build. Ones with '??', I dont know what they do or if they're required, feel free to tweak.

ro.ril.oem.ecclist=112,000,911	#changed
ro.ril.hsdpa.category=24	#changed
ro.ril.enable.amr.wideband=1	#changed
ro.telephony.default_network=0	#changed
ro.ril.fast.dormancy.rule=0	#changed, ??
ro.ril.radio.svn=2	#changed, ??
ro.ril.enable.sdr=0	#changed, ??
ro.ril.air.enabled=1	#removed, ??
ro.ril.enable.a52=0	#added, ??
ro.ril.enable.a53=0	#added, ??
ro.ril.disable.mcc.filter=1	#added, ??
ro.ril.emc.mode=1	#added, ??
ro.ril.oem.show.act=0	#added, ??
ro.com.google.clientidbase=android-htc
ro.com.google.clientidbase.yt=android-htc
ro.com.google.clientidbase.am=android-telstra-au
ro.com.google.clientidbase.gmm=android-htc
ro.com.google.clientidbase.ms=android-telstra-au
ro.product.model=HTC One XL
ro.config.htc.enableCOTA=0
ro.aa.project=Evita_UL
ro.aa.maincid=TELST001
ro.aa.cidlist=TELST001
ro.aa.modelid=PJ8312000,PJ8313000
ro.cwkey=TELST001
ro.build.id=[COLOR="Red"]IML74K[/COLOR]
ro.build.display.id=[COLOR="red"]IML74K[/COLOR]
ro.build.fingerprint=htc_asia_wwe/evita/evita:4.0.4/[COLOR="red"]IML74K[/COLOR]/82475.2:user/release-keys
[COLOR="Blue"]debug.composition.type=gpu	# Doubled up, earlier value is set to dyn[/COLOR]

The build ID 'IML74K' from build.prop shows up in the browser user agent string which is required for our Telstra web content to function. For ro.build.fingerprint, I left the line as per your config and just changed the build ID. This worked when I tested said content. It is possible that only the ua_string changes in MNS/default.xml were required but I did everything at once so can't be sure. For reference:

Stock telstra build (Works):

Mozilla/5.0 (Linux; U; Android 4.0.3; en-au; HTC EVA_UL Build/IML74K) AppleWebKit/534.30 (KHTML, like Gecko) Version/4.0 Mobile Safari/534.30

CleanROM 4.5 (Doesn't work):

Mozilla/5.0 (Linux; U; Android 4.0.4; en-us; PJ83100/1.82.502.3 Build/IMM76D) AppleWebKit/534.30 (KHTML, like Gecko) Version/4.0 Mobile Safari/534.30

Modified CleanROM 4.5 (Works):

Mozilla/5.0 (Linux; U; Android 4.0.4; en-au; HTC EVA_UL Build/IML74K) AppleWebKit/534.30 (KHTML, like Gecko) Version/4.0 Mobile Safari/534.30