One Main line coming to house but seperate modems

[wireless]

We have a telus line coming to our house, however it goes to the basement where they have the Telus internet. I'm living on the main floor and using Shaw but decided to switch to Telus, can I use that main line but have seperate modems? Will this affect the speed of the internet although both our plans are different? I've asked the basement dwellers and the refused to share the line as they fear they might get slow internet speeds, but the technician said it won't affect the speeds, so im now having to get a brand new Telus line put in, which is going to take some days due to the rainy weather atm. Would it really affect the speeds or basement dweller is just being paranoid?

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