snip Is this a technical fact or just a wishfull speculation? /
snip

It is a technical fact.

Both user equipment (your handheld mobile) and radio base stations
(what they talk to) have signal thresholds for "quality of service"
that must be met for normal calls (what you're paying for) to go
through. These thresholds are MUCH lower for text and emergency calls
for obvious reasons: text messages have no real-time requirements (and
much lower bandwidth requirements), and emergency calls are, well,
emergency calls; who cares about quality of service if it's an
emergency.

Additionally, normal calls are expected to use low uplink (transmit)
power levels on average, but they still require a lot more than text
messages. With modern mobile systems, power usage is EVERYTHING. If an
emergency call is placed (the system is 911-aware), this power
requirement is relaxed or ignored, in addition to the downlink
(incoming) signal-to-noise ratio thresholds.

-ted/2NO (former 3GPP Ericsson programmer)