What IMEI(s) does an ISP get in case I use a mobile hotspot to connect my laptop to the web?

I found out today that ISPs get the IMEI code of any device connected to them.

See a (very old) reference here: http://news.bbc.co.uk/2/hi/technology/4738219.stm

I was hence wondering: in case I connect to the web through a mobile hotspot with a prepay SIM card, which IMEI(s) does the ISP gets?

Say the setup is: Laptop – mobile phone – internet

Does the ISP get only the mobile phone IMEI, the laptop IMEI or both?