The following command should do what you want at a PowerShell command prompt on Windows:
Get-Content inputFile.sql | mysql -u username -p'password' DbName -h host.com.us | ForEach-Object { $_ -replace "\t","," } | Out-File outputFile.csv
Note that I've written the above out using the full names of the PowerShell cmdlets for clarity. One would typically use the aliases gc and % for Get-Content and ForEach-Object respectively.
A wrinkle that often catches me is that PowerShell uses a 16-bit Unicode encoding by default, so the outputFile.csv produced by the above example command line will be 16-bit Unicode. The Out-File cmdlet has an -Encoding parameter to allow you to make a different choice, such as UTF8. The above command could be rewritten as:
gc inputFile.sql | mysql -u username -p'password' dbName -h host.com.us | % { $_ -replace "\t","," } | Out-File -Encoding utf8 outputFile.csv
Edit: Changed password delimiters to single quotes to prevent PowerShell from attempting string interpolations.