[Moto G General] tpa-moto:
I can see that 8sms uses the same APN that is available in /etc/apns-conf.xml.

I downloaded a stock build for XT1031 and it seems that mcc="310" mnc="00" is either "Verizon CDMA HRPD" or "MetroPCS". I don't know why RIL is trying to set that numeric for Boost mobile.

These APNs were taken the stock build. I guess these make the dummy profile for Boost unneeded, either with "311870" or "31000" (ignore "carrier", that should be overridden by an eri file).

<apn carrier="Sprint"
mcc="311"
mnc="870"
type="default,mms,fota"
bearer="4"
protocol="IPV4V6"
roaming_protocol="IPV4V6"
authtype="3"
mmsc="http://mm.myboostmobile.com"
mmsproxy="68.28.31.7"
mmsport="80"
/>
<apn carrier="Sprint"
mcc="311"
mnc="870"
type="default,mms,fota"
bearer="5"
protocol="IPV4V6"
roaming_protocol="IPV4V6"
authtype="3"
mmsc="http://mm.myboostmobile.com"
mmsproxy="68.28.31.7"
mmsport="80"
/>
<apn carrier="Sprint"
mcc="311"
mnc="870"
type="default,mms,fota"
bearer="6"
protocol="IPV4V6"
roaming_protocol="IPV4V6"
authtype="3"
mmsc="http://mm.myboostmobile.com"
mmsproxy="68.28.31.7"
mmsport="80"
/>
<apn carrier="Sprint"
mcc="311"
mnc="870"
type="default,mms,fota"
bearer="7"
protocol="IPV4V6"
roaming_protocol="IPV4V6"
authtype="3"
mmsc="http://mm.myboostmobile.com"
mmsproxy="68.28.31.7"
mmsport="80"
/>
<apn carrier="Sprint"
mcc="311"
mnc="870"
type="default,mms,fota"
bearer="8"
protocol="IPV4V6"
roaming_protocol="IPV4V6"
authtype="3"
mmsc="http://mm.myboostmobile.com"
mmsproxy="68.28.31.7"
mmsport="80"
/>
<apn carrier="Sprint"
mcc="311"
mnc="870"
type="default,mms,fota"
bearer="12"
protocol="IPV4V6"
roaming_protocol="IPV4V6"
authtype="3"
mmsc="http://mm.myboostmobile.com"
mmsproxy="68.28.31.7"
mmsport="80"
/>
<apn carrier="Sprint"
mcc="311"
mnc="870"
type="default,mms,dun,fota"
bearer="4"
profile_id="1"
protocol="IPV4V6"
roaming_protocol="IPV4V6"
authtype="3"
mmsc="http://mm.myboostmobile.com"
mmsproxy="68.28.31.7"
mmsport="80"
/>
<apn carrier="Sprint"
mcc="311"
mnc="870"
type="default,mms,dun,fota"
bearer="5"
profile_id="1"
protocol="IPV4V6"
roaming_protocol="IPV4V6"
authtype="3"
mmsc="http://mm.myboostmobile.com"
mmsproxy="68.28.31.7"
mmsport="80"
/>
<apn carrier="Sprint"
mcc="311"
mnc="870"
type="default,mms,dun,fota"
bearer="6"
profile_id="1"
protocol="IPV4V6"
roaming_protocol="IPV4V6"
authtype="3"
mmsc="http://mm.myboostmobile.com"
mmsproxy="68.28.31.7"
mmsport="80"
/>
<apn carrier="Sprint"
mcc="311"
mnc="870"
type="default,mms,dun,fota"
bearer="7"
profile_id="1"
protocol="IPV4V6"
roaming_protocol="IPV4V6"
authtype="3"
mmsc="http://mm.myboostmobile.com"
mmsproxy="68.28.31.7"
mmsport="80"
/>
<apn carrier="Sprint"
mcc="311"
mnc="870"
type="default,mms,dun,fota"
bearer="8"
profile_id="1"
protocol="IPV4V6"
roaming_protocol="IPV4V6"
authtype="3"
mmsc="http://mm.myboostmobile.com"
mmsproxy="68.28.31.7"
mmsport="80"
/>
<apn carrier="Sprint"
mcc="311"
mnc="870"
type="default,mms,dun,fota"
bearer="12"
profile_id="1"
protocol="IPV4V6"
roaming_protocol="IPV4V6"
authtype="3"
mmsc="http://mm.myboostmobile.com"
mmsproxy="68.28.31.7"
mmsport="80"
/>

<!-- apn for Tracfone (VZW) -->
<apn carrier="Verizon CDMA HRPD"
mcc="310"
mnc="00"
type="default,mms,dun,supl"
mvno_type="spn"
mvno_match_data="Tracfone"
authtype="3"
mmsc="http://mms.vzwreseller.com/servlets/mms"
/>
<apn carrier="MetroPCS"
mcc="310"
mnc="00"
apn="internet"
server="*"
user="*"
password="*"
mmsc="http://mms.metropcs.net:3128/mmsc"
/>

<apn carrier="Verizon CDMA"
mcc="310"
mnc="004"
type="default,mms"
bearer="4"
protocol="IPV4V6"
authtype="3"
mmsc="http://mms.vtext.com/servlets/mms"
/>
<apn carrier="Verizon CDMA"
mcc="310"
mnc="004"
type="default,mms"
bearer="5"
protocol="IPV4V6"
authtype="3"
mmsc="http://mms.vtext.com/servlets/mms"
/>
<apn carrier="Verizon CDMA"
mcc="310"
mnc="004"
type="default,mms"
bearer="6"
protocol="IPV4V6"
authtype="3"
mmsc="http://mms.vtext.com/servlets/mms"
/>
<apn carrier="Verizon CDMA"
mcc="310"
mnc="004"
type="default,mms"
bearer="7"
protocol="IPV4V6"
authtype="3"
mmsc="http://mms.vtext.com/servlets/mms"
/>
<apn carrier="Verizon CDMA"
mcc="310"
mnc="004"
type="default,mms"
bearer="8"
protocol="IPV4V6"
authtype="3"
mmsc="http://mms.vtext.com/servlets/mms"
/>
<apn carrier="Verizon CDMA"
mcc="310"
mnc="004"
type="default,mms"
bearer="12"
protocol="IPV4V6"
authtype="3"
mmsc="http://mms.vtext.com/servlets/mms"
/>

Speaking of eri files, this is what I foundin the framework for values-mcc311-mnc870:

<?xml version="1.0" encoding="utf-8"?>
<resources>
<string name="config_mms_user_agent">motoXT1031 BOOST</string>
<string name="config_mms_user_agent_profile_url">http://device.sprintpcs.com/Motorola/XT1031-BOOST/motoxt1031.rdf</string>
<!-- more unknown stuff -->
</resources>

While this is what I get for values-mcc310-mnc00:

<?xml version="1.0" encoding="utf-8"?>
<resources>
<string name="config_mms_user_agent">motoXT1031 MVNO</string>
<string name="config_mms_user_agent_profile_url">http://device.sprintpcs.com/Motorola/XT1031-MVNO/motoxt1031.rdf</string>
</resources>

So 31000 is not that wrong after all, but there's no eri file for it.

Now I'm more confused than ever.

PS: I find interesting that in user agent file there's written you have MSM8626 as CPU rather than MSM8226.